Thermometer near me

Thermometer near me DEFAULT
  • The Thermapen One is our new upgrade pick (it’s available for preorder now, but won’t ship until mid-July). Our former upgrade pick, the ThermoWorks Thermapen Mk4, has been discontinued.

  • The Thermapen One is our new upgrade pick (it’s available for preorder now, but won’t ship until mid-July). Our former upgrade pick, the ThermoWorks Thermapen Mk4, has been discontinued.

    The new model looks very similar to the old version, but it has a few improvements. It provides incredibly accurate readings within just 2 seconds and it’s accurate +/- to half a degree. Its backlit screen is much brighter than the Mk4’s, and its newly designed battery compartment is more convenient to access if you need to adjust the settings. The Thermapen One also boasts a generous five-year warranty.

June 24, 2021

If you ever fret at the thought of accidentally serving your friends and family undercooked meat, eliminate your worry by getting a great digital meat thermometer. It’s one of the few tools that will instantly increase your confidence in the kitchen. After testing 36 digital instant-read and probe thermometers, we think the ThermoWorks ThermoPop is the best instant-read thermometer and the ThermoWorks Dot is the best probe thermometer for a home kitchen. Both thermometers are fast, accurate, and reasonably priced, with clear, easy-to-read displays.

On top of being fast and accurate, the ThermoWorks ThermoPop is also waterproof, and it’s designed to work for both righties and lefties. It can read temperatures ranging from -58 °F to 572 °F, and can easily switch between Celsius and Fahrenheit. The ThermoPop’s backlit display has large digits and rotates in four directions, so you can quickly read it from any angle. Although it’s not the fastest thermometer we tested, it comfortably covers most home-kitchen needs. And it is far, far better than most of the digital thermometers sold for less than $30.

If you want a thermometer that you can leave inside your roast while it bakes, or that you can attach to your grill or smoker, we recommend the ThermoWorks Dot. The Dot is accurate, affordable, and easy to use. It has the same wide temperature range as the ThermoPop, and it also has one of the longest probe cables of any of the thermometers we considered. The digital display on the ThermoWorks Dot is easy to read, and you can quickly set an alarm to go off when your meat reaches a certain temperature. We also like the backlit screen, which is handy for outdoor grilling at night.

The Lavatools Javelin Pro Duo instant-read thermometer is the midpoint option between the ThermoPop and the $100 best-in-class ThermoWorks Thermapen Mk4. In our tests, the Javelin Pro Duo was nearly a second faster at reaching a true temperature than the ThermoPop, and its folding probe lets you take readings from odd angles. It has a few features the ThermoPop lacks, such as a beep that tells you when it settles on a temperature, a button for holding the reading, and the ability to track minimum and maximum temperatures. It also displays temperatures down to a tenth of a degree. And unlike the ThermoPop or Thermapen, the Javelin Pro Duo has a magnet that lets you stick it to your fridge or stove, rather than keeping it loose in a drawer.

Upgrade pick

Thermapen ONE

Thermapen ONE

This was the fastest and most accurate instant-read thermometer we tested. It also offers a rotating screen with a bright backlight, a huge temperature range, and serious waterproofing.

Most people don’t need to spend over $100 on a thermometer. But if you care deeply about speed, or if you have cooking projects that demand to-the-degree accuracy, the ThermoWorks Thermapen One is the easy choice. This buttonless thermometer is completely automatic—it powers on when you pull out the probe, and the bright backlight and rotating screen are motion-activated. It was on average 2 to 3 seconds faster than the Javelin Pro Duo at reading temperatures in the mid-100s (Fahrenheit), where most cooking happens. Thanks to the thermometer’s long probe, you can be confident you’re getting readings from deep within your food.

If you’re looking for a few more helpful features on a leave-in probe thermometer, the ThermoWorks ChefAlarm includes a timer and volume adjustment. Though the ChefAlarm was a couple of seconds slower than the Dot at reading temperatures in our tests, it was just as accurate. We especially liked the convenience of the timer on this model. The digital unit is also hinged, so you can lay it flat or adjust it to a specific angle. Unlike our other picks, the ChefAlarm thermometer comes with a case to hold the probe and the digital unit.

Everything we recommend

Upgrade pick

Thermapen ONE

Thermapen ONE

This was the fastest and most accurate instant-read thermometer we tested. It also offers a rotating screen with a bright backlight, a huge temperature range, and serious waterproofing.

Why you should trust me

To find out what makes a great meat thermometer, I spoke with various food professionals, including barbecue and grilling expert Rick Browne, the creator, host, and executive producer of PBS’s Barbecue America series, and the author of more than 10 cookbooks; Janet Crandall, a private chef, formerly the executive chef and head butcher for Wyebrook Farm in Honey Brook, Pennsylvania, a butcher at Pat LaFrieda Meat Purveyors, and an instructor at the International Culinary Center (the ICC has since been acquired by the Institute of Culinary Education); and Robert D. Edman, assistant commissioner of the Bureau of Food Safety and Community Sanitation, New York City Department of Health.

As a senior staff writer for Wirecutter, I have written about everything from cookware sets to deep fryers. I’ve also spent 10 years working in the food and restaurant industry. My research builds on the work of former Wirecutter senior staff writer Kevin Purdy, who wrote the first version of this guide in 2013.

What type of meat thermometer should you get?

A person spooning pan sauce over a swordfish steak in a cast iron skillet, with a royal blue ThermaPen Mk4 resting to the side of the stovetop.

Every cook should have a reliable meat thermometer both to ensure food safety and to help you achieve the best results. The more common kind is an instant-read thermometer, which you stick into food for a few seconds to quickly check its doneness. Another type is a probe thermometer, which is designed to remain in the meat while it cooks. A heat-safe cable attaches the probe to a digital unit outside the oven that displays the temperature reading.

Most of the pros we spoke with recommended getting an instant-read thermometer over a probe thermometer. Probe thermometers are much slower to take an initial reading, so you can’t easily use one in place of an instant-read thermometer (our instant-read top pick takes 2 to 3 seconds, and our probe top pick takes 8 to 10). They also have a higher failure rate, because they’re constantly subjected to high heat.

The advantage of probe thermometers, however, is that you get an alert as soon as your meat reaches a set temperature, without having to open your oven door. This is especially useful for monitoring the doneness of a large cut of meat during a long roasting time, so you don’t accidentally overcook it. Just remember that different parts of a large cut of meat will cook at different rates, so even with a probe thermometer, it’s a good idea to use an instant-read thermometer to check your roast in a few different places. As barbecue and grilling expert Rick Browne told us, “The probe is sort of letting people know the temperature, and it’s a good guideline … then you can refine it with the instant-read and take multiple readings.”

Most of the pros we spoke with recommended getting an instant-read thermometer over a probe thermometer.

If you’re a seasoned cook and you have great instincts, you don’t truly need an instant-read or probe thermometer. But even professional chefs like taking the guesswork out of dishes, especially meats. For beginners in the kitchen, a good thermometer is a necessity to avoid overcooking steaks or undercooking fish or chicken, and for learning the baseline timing of your stovetop and oven.

A quick warning about induction cooktops

If you use an induction cooktop often, you’re likely to find that the electromagnetic field above the cooking surface can cause any digital thermometer that’s not specially shielded to read inaccurately or simply “crash” and fail to work at all. A Wirecutter reader and a pastry chef on the ChefTalk forums have both witnessed this effect, and mentions of the problem crop up elsewhere in Web searches. ThermoWorks, the maker of two of our picks, told us that induction cooktops are known to disrupt its devices. Thermometer maker CDN also acknowledges the problem.

One solution: You can temporarily turn off the induction cooktop while you take a reading; you lose very little heat and momentum by briefly halting an induction cooktop. The other alternative would be to use an analog thermometer, but as we mentioned before, those are slower and harder to read. We think that’s more likely to adversely affect the outcome of your food than turning off your induction cooktop to use one of our picks will.

How we picked

A collection of the thermometers we recommend, in a variety of colors.

For this guide, we tested the following types of thermometers, ranging from about $10 to $105:

  • Digital instant-read thermometers for quick readings
  • Basic probe thermometers with a single probe that stays in food as it cooks while displaying readings on a digital unit
  • Dual-channel probe thermometers with two probes, one for taking the internal temperature of the meat as it cooks and another for reading the ambient cooking temperature, while displaying readings on a digital unit
  • Remote probe thermometers that display readings on battery-operated wireless receivers or through smartphone apps via Bluetooth

Ultimately, we found that the digital instant-read and basic probe thermometers were by far the easiest to read and operate. Dual-channel thermometers are designed for grilling and smoker enthusiasts who want to monitor the temperature of their grill or multiple cuts of meat at the same time. Remote probe thermometers are for checking the progress of meat on a grill from inside your home. But we don’t think these extra features are useful for most people.

After testing more than 36 meat thermometers since 2013 and speaking with numerous experts, we’ve made a list of the most important features to look for when choosing a good instant-read or probe thermometer:

Speedy and accurate temperature readings: What matters most in a good kitchen thermometer is speed and clarity—how quickly you can turn it on and see a steady reading of the temperature inside your dish. A thermometer that can quickly jump toward the final temperature is much better than one that leaves you guessing as it slowly rises. Instant-read thermometers typically reach temperatures a few seconds faster than probe thermometers. In our tests, our top pick instant-read thermometer, the ThermoPop, reached temperatures in about 2 to 3 seconds, while our top pick probe thermometer, the Dot, took anywhere from 5 to 8 seconds. A good thermometer should also cover the whole temperature range of home cooking, from below freezing (32 °F) up past very hot frying oil (400 °F).

Sufficient probe length: The probe on a thermometer should be thin at its point to minimize juice-leaking punctures, and long enough to reach the center of large roasts or deep pots. A longer probe also helps keep your hands a safe distance from heat and steam.

Durable: A thermometer’s durability depends on how well its electronics are protected from dust and water, as measured by its IP (ingress protection) rating. The IP rating consists of two numbers that indicate how much abuse an item can withstand. The first number (ranging from 0–6) pertains to solids, and the second one (ranging from 0–8) pertains to liquids. For instance, the ThermoPop instant-read thermometer is rated IP66, which tells you that it’s “totally protected against dust” and “protected against strong jets of water.” The Dot probe thermometer is rated IP65, which means the body of the unit is protected against the entry of dust and “low-pressure jets of water.”

Easy to read: We prefer thermometers that display large numbers on their digital screens to make it easier to read temperatures quickly. Backlit displays are also convenient when you’re cooking in a dimly lit kitchen or grilling outdoors at night.

Reasonable price: With rare exceptions, we’ve found that thermometers retailing for $20 or less are slow, of poor quality, and often barely distinguishable copies of one another, so over the years we’ve narrowed our focus to thermometers that cost from $30 to $105. You can find some perfectly good thermometers at around $30 that are much faster and more durable than the cheapies. We think paying the extra $10 or $15 is worth it for an accurate, high-quality instrument, but paying a lot more isn’t necessary for most people.

Aside from the essential criteria outlined above, we also sought out a number of other features that we think good instant-read and probe thermometers should have.

For instant-read, thermometers we looked for:

  • Adjustable probes that make it easier to insert the thermometer at various angles.
  • Rotating screens (either manual or automatic) that let you easily see the temperature reading from different angles.
  • A strong magnet for storing the thermometer on the fridge. Note, however, that even though this is a nice feature, it’s not essential.

For probe thermometers, we looked for:

  • Heat-resistant cables (up to 700 °F) that are long enough so they won’t snag on an oven door or grill lid when closed.
  • A strong magnet for attaching the digital unit to the oven door.
  • Useful accessories, such as probe clips, which attach the thermometer to a saucepan when you’re frying oil or making candy.

How we tested

A collection of the thermometers we recommend, in a variety of colors.

To test and calibrate a thermometer, ThermoWorks and CDN both suggest filling a thick ceramic mug with ice, topping it off with water, and then checking the temperature. So we did just that and timed how quickly each instant-read and probe thermometer reached within 1 degree of the ice water’s 32 °F, from a starting temperature of around 65 °F. We did this four times and averaged out three of the results after we discarded the most uncommon timing (whether fast or slow).

A person testing the Thermoworks Dot by inserting the probe into a glass of ice water on top of a white towel.

We also timed how long each thermometer took to measure the temperature of canola oil heated in a cast-iron pot to 365 °F. Those timings were far slower and more unpredictable (10 to 20 seconds, instead of 2 to 5) for the instant-read thermometers we tested, but measuring hot oil did give us a sense of which thermometer best protected our hands.

The most useful test involved water that was heated with a sous vide circulator in a stock pot and kept to 130 °F. A good circulator keeps an entire pot of water at one consistent temperature—no hot or cold spots—so it’s an excellent tool to control accuracy. Precise temperature and circulation also seem to create the ideal environment for fast readings, because in our tests all the thermometers reached their target much quicker than they did in ice water or frying oil. Note: For our 2021 update, we did not test the ThermoWorks Thermapen One using a sous vide circulator since we were working from home during the pandemic.

We used each thermometer to either monitor or check the temperature (depending on the type of thermometer) of oven-baked chicken pieces, to get a feel for each one’s usability. For our original guide, we also used the instant-read thermometers to find the internal temperature of pork chops cooked sous vide and to measure the temperature of water inside an electric tea kettle. However, because neither of those tests gave us much additional insight, we opted not to repeat them for our subsequent updates.

We performed two additional tests for probe thermometers. To test their cables at high temperatures, we used our finalists in a screaming-hot, 650 °F to 700 °F grill. We also evaluated the strength of the magnets on the back of the digital receivers to see how well they could stay attached to the side of an oven or grill. Finally, we measured the distance at which remote probe thermometers could still function before losing their wireless connection.

Our pick for instant-read thermometer: ThermoWorks ThermoPop

An orange ThermoPop thermomether taking the temperature of a rack of lamb in an enameled cast iron braiser.

The ThermoWorks ThermoPop has been our top pick since 2015 because it reads temperatures quickly and accurately and comes at an excellent price. In our tests, it took the ThermoPop less than 4 seconds to land within 1 degree of most cooking temperatures. The large, rotating, backlit display is legible from almost any angle, and the long and thin probe gets into most roasts and liquids without exposing your hands to heat. In addition, the ThermoPop has a huge range (-58 °F to 572 °F), a splashproof body, one-button switching between Fahrenheit and Celsius, and an easy-to-access battery compartment.

In our tests, the ThermoPop measured the temperature of 130-degree water in an average of 3.49 seconds, and it was usually within a few degrees of that temperature in 2 to 3 seconds. For most people who just want to safely and properly prepare meats and delicate dishes without overcooking them, the ThermoPop does the job; getting a reading 1 to 2 seconds faster from our more expensive picks isn’t worth the extra money.

Besides speed, the ThermoPop’s screen is this thermometer’s strongest feature. The numbers are big and easy to read because the display doesn’t cram in a decimal point. The number rotates in four directions at the push of a button on the back, which helps when the probe is inserted sideways or diagonally into a hot or spattering dish. The rotating screen also makes the ThermoPop equally suitable for left- and right-handed use; this is not the case with many side-reading units, which favor the right-handed (though our other picks also have rotating screens). The screen’s backlight, which you can easily activate with the press of a button, is handy for grilling at night or taking a reading in a dark corner of the stove.

The ThermoPop’s 4½-inch-long probe is relatively generous compared with those of most of the thermometers we tested. The round head is also easy to hold and lets you get a secure grip. Even though you can’t adjust the angle of the probe, we found that it’s long enough to stab into many sections of a roast or dish without risking burning your fingertips.

The whole thermometer is rated IP66 resistant: completely impervious to dust and able to withstand “high pressure water jets from any direction.” That means you don’t need to worry about getting the probe wet when you wash it, which you should do—but you should not go so far as to stick it in the dishwasher. Automatic shut-offs on both the backlight and the thermometer itself help extend its battery life. Compared with battery replacement on most cheap thermometers, on the ThermoPop it’s a cinch: Put a regular-size screwdriver into the back and twist, pop in a new watch battery (CR2032), turn the cover back on, and go.

The ThermoPop covers temperatures from -58 °F to 572 °F (-50 °C to 300 °C), which is the widest range of any instant-read thermometer below $50 that we’ve found. You can choose your ThermoPop in one of nine colors, and each one comes with a laminated guide to cooking temperatures that covers not only food-safety temperatures but also sugar stages for candy making, as well as every level of doneness for beef and pork (you can grab the PDF at ThermoWorks’s site). It’s a handy thing to stick on your fridge or to keep in a drawer.

The ThermoPop comes with a two-year warranty on the digital unit and a six-month warranty on the probe (the probes can be replaced if damaged). Keep in mind that the warranty is valid only if the product is purchased from ThermoWorks directly or from an authorized reseller (which does not include Amazon).

Flaws but not dealbreakers

You can’t adjust the angle of the ThermoPop’s stick-style probe as you can with a fold-out thermometer like the Thermapen One. Although we don’t think this design is a dealbreaker, we’ve encountered certain instances—such as taking the temperature of meat on a scorching-hot grill—where we’ve wished we could angle it to get our hands a little farther away from the heat.

A closeup of the back of the ThermoPop thermometer.

On the device itself, the water-resistant buttons are a little small and hard to press, especially for people with big fingertips. Sometimes we had to press a button twice to be sure it activated.

Unlike the Javelin Pro Duo, the ThermoPop lacks a magnet to keep it stuck to metal surfaces or appliances. Although this is a feature many people won’t miss, without it you’ll need to keep the thermometer in a drawer, where it might be trickier to find.

As we mentioned earlier, the ThermoPop reads in whole numbers, not to the tenth of a degree, as most of the above-$20 competition does. But this model’s level of accuracy should be sufficient for most cooks, and it’s a trade-off for clear digits that rotate.

Our pick for probe thermometer: ThermoWorks Dot

The ThermoWorks Dot sitting on a wooden countertop next to a silver sheet pan.

If you want to monitor the doneness of a piece of meat as it cooks, we recommend the affordable ThermoWorks Dot probe thermometer for its impressive accuracy and ability to read temperatures quickly. Compared with the other probe thermometers we tested, it was the easiest to use, thanks to its simple, intuitive design and large digital display. The Dot’s wide temperature range makes it ideal for both oven and grill use, and its backlit screen makes it easy to read in any light.

In our tests, the Dot was the fastest probe thermometer to read temperatures accurately. On average, it was able to read 32 °F in about 8½ seconds and 212 °F in about 5.5 seconds. Its thermistor sensor has an impressive temperature range of -58 °F to 572 °F (and a cable that can withstand 700 °F for short periods of time), which is a wider range than many other probe thermometers cover. In a stockpot of 130 °F water maintained by a sous vide circulator, the Dot was accurate to the degree.

The Dot also had one of the longest cables—about 48 inches—of the probe models we tested. The cable became slightly discolored and stiff when we subjected it to the high heat of a grill. But that had no effect on the thermometer’s performance (however, ThermoWorks states that the Dot should not be used when broiling in the oven). Also, the Dot’s 4½-inch probe will have no problem reaching the center of large roasts.

A person holding the ThermoWorks Dot, displaying the magnets and plastic stand on the back.

The Dot’s simple design and straightforward controls made it easier to use than the competition. This model has an on/off switch on the back of the unit, with arrow buttons on the side of the digital screen that allow you to set your desired temperature. After you insert the probe into your food, the alarm beeps to let you know when the set temperature has been reached. You can press any button on the interface to stop the alarm; to disable the alarm altogether, simply hold the two arrows down at the same time. You can also switch from Fahrenheit to Celsius by holding the power button for 6 seconds while turning on the unit. And among the probe thermometers we tested, the Dot has some of the strongest magnets, which kept it securely attached to the side of our oven.

The ThermoWorks Dot boasts an Ingress Protection rating of IP65, which means the body of the unit is protected against the entry of dust and “low-pressure jets of water.” Like the ThermoPop, the Dot is available in a variety of colors. It also comes with a two-year warranty, and the probe is replaceable.

This model is also available with Bluetooth, sold under the name BlueDot, for about $26 more. It has all of the same controls as the regular Dot thermometer, but it can also connect to an app on your phone, which allows you to monitor the food you’re cooking from a short distance. It’s a nice added feature, but we think most people will be happy without it.

Flaws but not dealbreakers

We’ve received feedback from a few readers saying the Dot began to malfunction after only several months of use, though we haven’t experienced this with the two models we’ve been long-term testing for two years. If you notice the Dot has become glitchy or less responsive, we’d recommend reaching out to ThermoWorks as soon as the problem arises. Probe thermometer wires take a beating, so if you’re experiencing issues, it may be that the wire is damaged and needs to be replaced. Improper readings may also be caused by a low battery charge, so we’d try replacing them to see if it solves the issue (it takes two AAA batteries).

The ThermoWorks Dot doesn’t come with a metal clip to attach the probe to the side of a saucepan for tasks such as frying or candy making, but all ThermoWorks accessories (including probe clips, grate clips, and air probes) are sold separately.

The Dot also lacks a timer and preprogrammed temperature settings for certain types of meat. However, since the pros we spoke with don’t recommend using preset temperatures anyway, we don’t think this omission is a dealbreaker.

Also great: Lavatools Javelin Pro Duo

Upgrade pick: ThermoWorks Thermapen One

The Thermapen One

Upgrade pick

Thermapen ONE

Thermapen ONE

This was the fastest and most accurate instant-read thermometer we tested. It also offers a rotating screen with a bright backlight, a huge temperature range, and serious waterproofing.

What makes the ThermoWorks Thermapen One worth a cool $105 plus shipping? Mainly, it’s the fastest instant-read thermometer we’ve ever tested. The Thermapen One replaced the now-discontinued Thermapen Mk4, which was our long-time upgrade pick and a favorite of culinary pros. The Thermapen One is very similar to the Mk4, with a few improvements. Its needle-sharp probe is even faster and more accurate at reading temperatures (averaging about 1.5 seconds in our tests), and it is thin enough to slide easily into the thinnest of fish fillets or pounded chicken breasts. Its backlit screen is also noticeably brighter and easier to read than that of its predecessor. The display automatically turns on when you pick the thermometer up (if the probe is extended), and it rotates in four directions as you change the angle of the thermometer. The Thermapen One is by no means necessary for most cooks, but it’s an indispensable tool for those who love the science of cooking or the pursuit of kitchen perfection.

The Thermapen One above the discontinued Thermapen Mk4.

What’s most impressive about the Thermapen One is how much closer it gets to the final temperature in the early stages of its reading. Almost instantly, it knows that your 160 °F chicken is at least 150 °F. Within 2 seconds, it has a reading that's 1 or 2 degrees away. That kind of speed means you can get food off the heat quicker if you know it’s going too far, or you can be certain to turn down your frying oil. The Thermapen One’s range is -58 °F to 572 °F (about -50 °C to 300 °C), the same as the ThermoPop’s.

The Thermapen’s fold-out probe is 4½ inches long, and it’s 1 millimeter thinner than the ThermoPop’s 3-millimeter probe tip; when fully extended, it puts you a good 10½ inches from anything hot. The Thermapen’s IP67 rating means it’s totally protected against dust, and it can withstand a dunk in water for up to 30 minutes, as long as you don’t twist it around while it’s submerged. It can certainly survive some splashed barbecue sauce or spilled drinks.

The Thermapen One lets you choose between Fahrenheit and Celsius, and whether you want a decimal reading, but you’ll need a small Phillips head screwdriver to access the switches. Photo: Michael Sullivan

The Thermapen One next to the Thermapen Mk4.

The Thermapen One (left) has a battery compartment that’s easier to access than the now-discontinued Thermapen Mk4 (right). Photo: Michael Sullivan

A Thermapen shown with the end removed, so that the thermometer can be switched between Fahrenheit and Celsius readings.

The older Thermapen Mk4 had a tighter battery compartment that made it more difficult to adjust the settings. Photo: Sarah Kobos

Inside the Thermapen One there’s a single AAA battery, which lasts for a very long time (the Mk4 also used a AAA battery and it lasted at least a year in our kitchen). The biggest visible difference between the Thermapen One and the Mk4 is the new battery compartment, which is larger and easier to access. The compartment still contains switches that let you disable the automatic shutoff or screen rotation, switch between Fahrenheit and Celsius, and choose whether the Thermapen shows a decimal point.

Having those switches inside the battery compartment is something of an inconvenience if you need to change between Celsius and Fahrenheit more than once in a while. While it’s easier to do so than it used to be on the Mk4, you still need to unscrew the battery cover to access the menu and set buttons.

On top of that, it would be an improvement if the thermometer had a magnet for hanging it on something like a fridge. Since the Thermapen One is a slightly different shape than the Mk4, it won’t fit ThermoWorks’s magnetic case (though a new one will be available soon). However, according to the ThermoWorks representative we spoke to, other accessories like the wall bracket and zipper wallet will still work.

The major technology difference between the Thermapen and its competitors is its thermocouple sensor. The majority of instant-read thermometers (including the Lavatools Javelin Pro Duo, our mid-level upgrade) use a thermistor, a small, relatively cheap but accurate resistor bundle stored in the tip of the probe. The Thermapen’s thermocouple has a thin sensor wire running down its whole probe, and the thermometer also keeps a more extensive set of reading and calibration electronics inside its sizable body. Because the wire has less mass than a thermistor module, it registers changes in temperature more quickly. That thin wire also allows for a thinner probe, which is helpful for piercing thin fish fillets and reducing the size of juice-releasing punctures.

ThermoWorks has made improvements to the Thermapen One’s construction that allow it to read faster than previous models, giving it an increased accuracy of ± 0.5 °F (compared with the Mk4’s ± 0.7 °F). The Thermapen One comes with a certificate of calibration from ThermoWorks’s NIST-traceable lab, which means it meets certain industrial regulations and standards of performance. It’s unlikely that you’ll ever need to recalibrate the Thermapen One. But according to the representative we spoke to, you can press and hold the menu button (located in the battery compartment) while the thermometer is turned on, and adjust ±3.6 degrees Fahrenheit using the set button. When you have the desired value selected, the menu button will save it.

If you wanted to save about $20, you could buy the “classic” Thermapen. It’s not as fast at reading temperatures and it lacks the rotation and display upgrades and sticks to a coin battery. We think the Thermapen One’s conveniences are worth the full cost. It also comes with an impressive five-year warranty, which is an improvement over the Thermapen Mk4’s two-year warranty.

Also great: ThermoWorks ChefAlarm

The ChefAlarm probe thermometer on a kitchen counter.

If you want more features in a probe thermometer, such as a timer and volume adjustment, we recommend the ThermoWorks ChefAlarm. It was very accurate in our tests and has a longer probe than the Dot, but we found that it was slightly slower at reading temperatures. The ChefAlarm offers the same impressive temperature range as the Dot, from -58 °F to 572 °F for the probe and up to 700 °F for the cable.

In our tests, the ChefAlarm took a couple seconds longer than the Dot to read temperatures, but it was just as accurate. The timer on this model is a nice addition (it can handle countdowns as long as 99 hours, 59 minutes), and the backlit screen is handy for outdoor grilling at night. The ChefAlarm also allows you to set the minimum and maximum temperatures, which have corresponding alarms to alert you when they’ve been reached.

The two strong magnets on the back of the unit keep it in place when attached to the side of an oven or grill; the digital unit is also hinged, so you can lay it flat or adjust it to a specific angle. We like that the ChefAlarm thermometer comes with a case to hold both the probe and the digital unit. However, in spite of the ChefAlarm’s various benefits, we think most people will be fine with the Dot.

Tips for using your thermometer accurately

Regardless of which type of meat thermometer you use, keep in mind that the probe measures only the area of the meat it’s touching. You need to know where to place the probe to correctly measure the internal temperature of the meat—a challenge, particularly for beginner cooks.

According to Robert D. Edman, assistant commissioner of New York City’s Bureau of Food Safety and Community Sanitation, “The probe should be inserted into the thickest part of the meat, poultry, or poultry parts, away from bone, fat, or gristle. When taking the temperature of beef, pork, or lamb roasts, the probe should be inserted midway into the roast, avoiding the bone. The core temperature is what is being determined.” (Chef Janet Crandall told us that bones conduct more heat and will give you a higher temperature reading.)

For thinner proteins, such as fish fillets, insert the probe sideways. If you’re uncertain about the proper placement or final temperature of the meat you’re cooking, most of the pros we spoke with recommended taking multiple readings using an instant-read thermometer.

Care and maintenance

Before you use any thermometer, “you should always make sure [it is] calibrated,” said Crandall. “A thermometer should read 32 °F in ice water, and 212 °F in boiling water.” Most thermometers come calibrated, but it’s still good to double-check before using.

Never put the digital unit of a thermometer in an oven, grill, or smoker, or attach it to the lid of a grill, which can exceed 700 °F and melt it. Though the ThermoWorks probe thermometer cables are heat-resistant to 700 °F, avoid placing them directly on a grill grate or oven rack, since doing so could damage their inner insulation. Also, straighten any kinks in the cable, which can break the inner wires if left alone. And never place a probe tip directly into hot coals or fire. Always use a hot pad or an oven mitt when retrieving a probe thermometer from the oven or grill.

To prevent cross-contamination, be sure to properly sanitize the probe after each use, washing it thoroughly with dish soap and hot water.

The competition

Honorable mention: A feature-loaded probe thermometer

Like the ChefAlarm, the ThermoWorks Smoke has a backlit screen and volume control. But in contrast to our other picks, the Smoke can operate via a wireless receiver and has two channels to accommodate multiple probes: one probe to take the internal temperature of the meat, and an air probe for measuring the ambient temperature of the oven, grill, or smoker. The Smoke also allows you to set the minimum and maximum temperatures for each probe, and will sound corresponding alarms when the set temperatures have been reached. In our tests, the Smoke maintained its wireless connection for an unobstructed distance of 350 feet, more than double the distance of the Weber iGrill 2. But considering that this thermometer is also $60 more than the ThermoWorks Dot, we think it makes sense only for grill and smoker enthusiasts.

If you want to monitor the Smoke’s probes from any distance, ThermoWorks also offers the exorbitantly priced Smoke Gateway, which pairs with Wi-Fi to allow you to get alerts from the Smoke on your phone. We tried out the Smoke Gateway and thought it worked fine, but we think it’s a pricey convenience item that most people can do without.

Instant-read thermometers

The Lavatools Javelin was previously our runner-up pick, but after some consideration we concluded that it didn’t hold a candle to the ThermoWorks ThermoPop in terms of the most useful features. The Javelin has a notably shorter probe, and it’s not as waterproof as the ThermoPop. Also, its display does not rotate or light up.

The OXO Good Grips Thermocouple Thermometer, which costs about the same as the Thermapen Mk4, did very well in our tests and read temperatures in about 2 seconds. Because its digital screen always stays illuminated, it’s especially easy to read, but the digits rotate in only two directions (whereas the digits on the ThermoPop and the Thermapen rotate in four directions). At 4⅛ inches, the OXO’s probe is slightly shorter than those of the ThermoPop and the Thermapen, so it can’t reach quite as deep into large cuts of meat. The OXO is rated IP66 (versus the Thermapen Mk4’s rating of IP67). If you’re willing to spend $100 on a thermometer, we think you’re better off getting the Thermapen Mk4 over the OXO because the Mk4 performed better in our tests overall and has an excellent track record.

We had issues understanding the readings we got with the Maverick PT-50. We used the calibration button to set it to ice water (a standard calibration method), but it was still not as fast as any of our picks. After that, it refused to rise near the temperature of the 130 °F water, so we dismissed it.

The factory-calibrated, Thermapen-like Maverick PT-100 was glacial in testing ice water (taking nearly 11 seconds), and it read lower than all of the other thermometers in our sous vide test. Readings aside, the Maverick PT-100 doesn’t offer a lot of helpful features, and it’s strangely less dustproof and waterproof (IP44) than most of the thermometers we’ve tested.

Taylor’s 9867 Digital Folding Probe Thermometer has an interesting design, but it landed in the middle between our picks and cheaper models. Its display is bright, and its probe tip, at 1.5 millimeters, is thinner than the Thermapen’s. It’s not a bad thermometer, but its digital screen doesn’t rotate, unlike the ThermoPop’s. We think it’s worth spending a couple of dollars more on the ThermoPop for the convenience that feature provides.

Our prior runner-up pick, the Polder Stable-Read, kept pace with our picks in an early 2016 test. It issued a helpful beep when it reached a stable reading (or at least when it determined that it had), and it was a bit cheaper than the ThermoPop. But it’s not often in stock on Amazon. If you like a stick-style thermometer, it’s a decent pick, but the ThermoPop suits more people.

The Palermo Digital Food Thermometer is the most affordable fold-out-style thermometer we found. It has a very wide range (up to 572 °F), and a stated 0.9-degree accuracy. It does not, however, reach within 1 degree of boiling water in 4 to 5 seconds, as the company states; we found that it took at least 12 seconds in three different trials.

The CDN DTW450L ProAccurate Waterproof Thermometer claims, right on its Amazon page, a 6-second response time, and in our first chicken test it averaged 6.13 seconds. It has an 8-inch probe, which is so long that we constantly feared it would snap.

The Taylor 9842 Commercial Waterproof Digital Thermometer has a good range (-40 °F to 450 °F), essentially mediocre speed ratings (although notably slower on ice water), and a calibration screw. It’s the best thermometer you can get for about $10, but that’s not what most people are looking for.

The AcuRite 00665E Digital Instant Read Thermometer is an inexpensive thermometer in the fold-out style of the Thermapen. It felt cheap to use—the buttons seemed to require mashing, and the probe was not particularly thin. And this thermometer always took at least 10 seconds to get hot or cold temperatures—sometimes up to 19 seconds.

The Lavatools Element was very slow at reading temperatures, taking up to 15 seconds in some instances. The temperature readings don’t gradually increase, either, jumping from number to number, which makes it difficult to anticipate temperature changes. Its digital controls aren’t as intuitive to use as our picks’, and the buttons are very difficult to press.

We found the receiver of the ThermoPro TP20 difficult to read because it alternated the display of both probe temperatures, which we found confusing. The membrane-sealed push button on the receiver also became worn after only a few uses.

Since the ThermoPro TP16 is so light and the cable is so stiff, the unit moved around the counter when we opened and closed the oven door. We also found that the stand put the digital screen at an awkward angle for reading.

The Maverick ET-733 suffered notable delays in reading temperatures. In one instance, the thermometer jumped from 73 °F to 214 °F, showing no temperatures in between. This model is also covered by a paltry 90-day warranty.

Although the Taylor 1478-21 Digital Cooking Thermometer has intuitive buttons and a simple design, it’s slow at reading temperatures. It also can’t work on a hot grill because the cable and probe are heat-resistant to only 392 °F.

Good (but pricey) probe thermometers with wireless capability

The ThermoWorks Signals 4-Channel BBQ Alarm Thermometer is essentially the next step up from the ThermoWorks Smoke. It comes with four probes (one is an air probe) instead of two, all of which you can use simultaneously. It can also connect to an app on your phone via Bluetooth or Wi-Fi, which is nice if you’re smoking meat and you want to monitor its progress from inside. But at $230, this four-channel thermometer is overkill unless you’re on a competitive barbecue team, or if you regularly cook several cuts of meat at once.

The ThermoWorks BlueDot is the same as the ThermoWorks Dot we recommend, except it can connect to an app on your phone via Bluetooth, which allows you to monitor the food you’re cooking from a distance. ThermoWorks advertising says the BlueDot can stay connected for an unobstructed distance of 95 feet, but in our tests it lost the connection at around 75 feet. We think most people will be happy with the Dot, which currently costs about $20 less.

Not-so-good probe thermometers with wireless capability


Rite Aid Digital Thermometer with Flexible Tip

Item No. 8012023

Every home needs a thermometer, but with so many on the market, which do you choose? Rite Aid's Fast Read Digital Thermometer is always the one to go with! It's three-times faster than regular thermometers and there's no need to worry about broken glass or mercury poisoning. This fever thermometer will give you clinically accurate readings in 20 seconds and can display those readings in either Fahrenheit or Celsius. The extra large display makes it easy to read, and the memory recall allows you to check the last temperature taken to measure progress. The thermometer will beep when the reading is ready. Maybe most importantly, it has a built in fever alarm that will alert you immediately if a temperature over 99.5 degrees Fahrenheit is detected. Rite Aid's digital thermometer may be used for oral or rectal temperature taking. Each thermometer comes with one 1.55V DC button battery, a protective case, 5 free probe covers, instructions, and warranty information.

Features & Benefits:

  • Soft, flexible tip
  • Fever alarm
  • 3 times faster than regular thermometers
  • Large digital display
  • Recalls last temperature taken
  • Readings in Fahrenheit or Celsius
  • Protective case and battery included

Thermometers are eligible for FSA and HSA reimbursment. For any questions you may have regarding FSAs or HSAs, please browse our FAQ.
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Your medicine cabinet should always include a good working thermometer. This is especially true during the COVID-19 pandemic as fever is one of the first signs of coronavirus infection.

If you think you’ve been exposed to the virus, keeping track of your temperature can help prevent the spread of COVID-19 in your home and outside.

“The earlier you know if you have fever, or any other COVID-19 symptom, the quicker you can isolate yourself from others and contact your doctor,” says Ghazala Sharieff, MD, MBA, Scripps chief medical officer, clinical excellence and experience.

Why is fever a key symptom?

Fever is a key symptom because it indicates that your body is trying to fight an illness or infection.  

Fever is defined as temperature of 100.4 Fahrenheit or above. Normal body temperature can range from 97 F to 99 F. 

Does a fever mean I have COVID-19?

Don’t rely only on temperature screening to determine whether you have COVID-19. You must watch for other symptoms of coronavirus, including shortness of breath, coughing, fatigue, headache and loss of taste or smell. Coronavirus symptoms may appear 2-14 days after exposure to the virus, according to the Centers for Disease Control and Prevention (CDC). 

“Only further evaluation and diagnostic testing can determine if someone has COVID-19 or something else,” Dr. Sharieff says.

There may be other causes for your fever, including the common flu or a bacterial infection, such as strep throat. Also, you may not get an accurate temperature reading if you have taken a fever-reducing drug.

What is the best thermometer?

All thermometers are designed to give you an accurate temperature reading and must meet federal standards before they can be sold in the United States. 

There are different types of thermometers — including digital, non-contact and mercury. You may have one of these already or may be shopping around for one online or at your local pharmacy. You have choices though price and availability should be considered.

You may prefer a certain type or age-appropriate thermometer, especially if you have young children. You may be interested in a special feature. For example, non-contact thermometers are in demand during the COVID-19 pandemic.

Whatever thermometer you plan to use, make sure to follow the specific instructions for using and cleaning it.

What is a no-touch thermometer?

No-touch or non-contact infrared thermometers measure temperature through the forehead from a close distance in seconds. They may be used on newborns and older people.

They’re easy to use and may reduce the risk of spreading disease by allowing more physical distancing. 

With this thermometer, you aim the device about an inch or so from a person’s forehead, press the scan button and watch for the temperature reading on the thermometer screen. Face masks are advised if you’re taking the temperature of someone who may be infected.

It’s important to note that no-touch thermometers are slightly less accurate than internal thermometers, which are the gold standard in healthcare.

What is a temporal artery forehead thermometer?

Temporal artery thermometers work by sliding the device over the forehead. They read the infrared heat waves released by the temporal artery, which is close to the surface of the skin. Remember to clean and disinfect the thermometer in between uses.

What is a tympanic (ear-mode) thermometer?

A tympanic infrared thermometer is an ear thermometer that measures temperature in the ear drum. It’s important to place the device correctly and make sure there is no ear wax in the way. Pediatricians advise against using an ear thermometer on infants younger than 3 months.

Digital thermometers

Regular digital thermometers also use sensors to measure body temperature. These thermometers have varieties that can be placed in the rectum, mouth or armpit. They read temperature when the sensor located on the tip of the thermometer touches that part of the body.

The following thermometers are recommended as your child grows:

  • Under 3 years: rectal
  • 4 to 5 years: rectal, oral, armpit, tympanic
  • 5 years to adult: oral, armpit, tympanic

Rectal thermometers are recommended for newborns and children up to age 3. Comfort and safety features like a flexible tip and wide base are recommended.

Armpit thermometers are not considered as accurate as other types of thermometers but can be helpful if you are unable to take your child’s temperature another way.

Oral thermometers are recommended for children 4 and over and adults. It's important to keep your mouth closed while the thermometer is in place. 

Do not use a digital thermometer to take both oral and rectal temperatures.

Mercury thermometer

Mercury thermometers were once widely used but are no longer recommended because they can break, and toxic mercury can escape.


With everything that’s happened over the past year, renewed importance has been placed on taking your temperature regularly. It’s a fast, easy, and affordable way to keep tabs on your health, especially in these days of COVID-19. While oral thermometers are reliable, non-contact models (like the ones we’ve reviewed here) are better for rapid temperature checks and large groups of people, as they can give you faster, more accurate results without the chance of spreading germs.

Check out quick info below on the top five contactless thermometers, then scroll deeper for full reviews of these models plus other high-ranking options.

Best Overall

iHealth No-Touch Forehead Thermometer

iHealth No-Touch Forehead Thermometer


Consumer Score: 82% gave it 4 stars or more

Glowing reviews praise the design and ease of use. 

For Family Use

iProven NCT-978

iProven NCT-978


Consumer Score: 90% gave it 4 stars or more

Quick reading, and accurate every time.


Withings Thermo Smart Temporal Thermometer

Withings Thermo Smart Temporal Thermometer


Consumer Score: 88% gave it 4 stars or more 

Keep track of your temp over time.  


Vibeey Infrared Digital Thermometer

Vibeey Infrared Digital Thermometer


Consumer Score: 85% gave it 4 stars or more

For a low cost, you can detect a high temperature.

For Small Businesses

Gekka Wall-Mounted Infrared Forehead Thermometer

Gekka Wall-Mounted Infrared Forehead Thermometer


Consumer Score: 78% gave it 4 stars or more

Placed on the wall, ready for high traffic.

How We Selected and Rated Them

To determine the best non-contact thermometers, we researched expert sources such as Health, Forbes, and Tom’s Guide, as well as 26,000 consumer reviews. Our Consumer Score represents the percentage of customers who rated the product at least four out of five stars on retail and review sites like Amazon,Walmart, and manufacturers’ webpages.


iHealth PT3

Consumer Score: 82% gave it 4 stars or more
Glowing reviews praise the design and ease of use.




  • Sleek design
  • Easy to read

This model topped many a list of the best non-contact thermometers. And while it has a sleek and sophisticated design, it uses three sensors to give you an accurate reading every time. iHealth built in a large, easy-to-read screen, and the PT3 will vibrate as a quick indicator that it’s done grabbing the temperature. Bonus: It comes with a one-year warranty and batteries included.


iProven NCT-978

Consumer Score: 90% gave it 4 stars or more
Quick reading, and accurate every time.




  • Affordable
  • Color-coded alerts

This affordable option is great for families as it reads temperatures of every age with impressive accuracy. The NCT-978 takes one second to read—ideal for fussy children—and uses color and sound alerts if it picks up a high temperature. It can work from up to two inches away.


Withings Thermo Smart Temporal Thermometer

Consumer Score: 88% gave it 4 stars or more
Keep track of your temp over time.

Thermo Smart Temporal Thermometer



  • Works quickly
  • Tracks temperature over time

If you want as much info as possible, get this smart thermometer. It takes an accurate reading in two seconds when you hold it close to the temple and sends the result to an app on your phone. The app will then store your temperature and is able to keep track of your results over time so that you can see trends and recognize when something is off. (You can plug in any medications you may be taking, as well.) And it can do that for up to eight people if you want to log temps for a family.


Vibeey Thermometer

Consumer Score: 85% gave it 4 stars or more
For a low cost, you can detect a high temperature.

Infrared Digital Thermometer


  • Affordable
  • Color-coded temperature display

Most of us don’t want to shell out more than $40 for a thermometer. Good then that this one is under $20 and has some great features, including color indication (red for fever, yellow for high temperature), and can accurately take the temperature of all of your family members, infant to elderly. The display is large and bright, which makes it easy to read, and it’s small enough to slip in a bag or backpack if you need to take it with you.


Gekka Wall-Mounted Infrared Forehead Thermometer

Consumer Score: 78% gave it 4 stars or more
Placed on a wall, ready for high traffic.

Gekka Wall-Mounted Infrared Forehead Thermometer



  • Works great in offices or high-traffic areas
  • Easy to read

This thermometer is designed for reading many temperatures quickly. To that end, you can fix it to a wall for ease of use, say near an entrance to a store or office. It takes temperatures in less than a second so long as it’s within four inches of the subject—plus, it will flash red and set off an alarm if someone’s temp is higher than normal. It runs on batteries or charging via a USB. Some reviewers noted that it wasn’t 100 percent accurate, but it’s close enough (within a degree or two) to let you know when a temperature is above normal.

Gabrielle HondorpBefore joining Runner's World as an Editor in 2019, Gabrielle Hondorp spent 6 years in running retail (she has tested top gear from shoes, to watches, to rain jackets which has expanded her expertise—and her closets); she specializes in health and wellness, and is an expert on running gear from head-to-toe.


Me thermometer near


Device to measure temperature

For broader coverage of this topic, see Temperature measurement.

A thermometer is a device that measures temperature or a temperature gradient (the degree of hotness or coldness of an object). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb of a mercury-in-glass thermometer or the pyrometric sensor in an infrared thermometer) in which some change occurs with a change in temperature; and (2) some means of converting this change into a numerical value (e.g. the visible scale that is marked on a mercury-in-glass thermometer or the digital readout on an infrared model). Thermometers are widely used in technology and industry to monitor processes, in meteorology, in medicine, and in scientific research.

Some of the principles of the thermometer were known to Greek philosophers of two thousand years ago. As Henry Carrington Bolton (1900) noted, the thermometer's "development from a crude toy to an instrument of precision occupied more than a century, and its early history is encumbered with erroneous statements that have been reiterated with such dogmatism that they have received the false stamp of authority."[2] The Italian physician Santorio Santorio (Sanctorius, 1561-1636)[3] is commonly credited with the invention of the first thermometer, but its standardisation was completed through the 17th and 18th centuries.[4][5][6] In the first decades of the 18th century in the Dutch Republic, Daniel Gabriel Fahrenheit[7] made two revolutionary breakthroughs in the history of thermometry. He invented the mercury-in-glass thermometer (first widely used, accurate, practical thermometer)[2][1] and Fahrenheit scale (first standardized temperature scale to be widely used).[2]


Main articles: Temperature and Temperature measurement

While an individual thermometer is able to measure degrees of hotness, the readings on two thermometers cannot be compared unless they conform to an agreed scale. Today there is an absolute thermodynamic temperature scale. Internationally agreed temperature scales are designed to approximate this closely, based on fixed points and interpolating thermometers. The most recent official temperature scale is the International Temperature Scale of 1990. It extends from 0.65 K (−272.5 °C; −458.5 °F) to approximately 1,358 K (1,085 °C; 1,985 °F).

Early developments[edit]

See also: Thermometry, Temperature scale, Thermoscope, Alcohol thermometer, and Timeline of temperature and pressure measurement technology

Fifty-degree thermometers from the mid-17th century on exhibit at the Museo Galileowith black dots representing single degrees and white represented 10-degree increments; used to measure atmospheric temperatures

Various authors have credited the invention of the thermometer to Hero of Alexandria. The thermometer was not a single invention, however, but a development. Hero of Alexandria (10–70 AD) knew of the principle that certain substances, notably air, expand and contract and described a demonstration in which a closed tube partially filled with air had its end in a container of water.[8] The expansion and contraction of the air caused the position of the water/air interface to move along the tube.

Such a mechanism was later used to show the hotness and coldness of the air with a tube in which the water level is controlled by the expansion and contraction of the gas. These devices were developed by several European scientists in the 16th and 17th centuries, notably Galileo Galilei[9] and Santorio Santorio.[3] As a result, devices were shown to produce this effect reliably, and the term thermoscope was adopted because it reflected the changes in sensible heat (the modern concept of temperature was yet to arise).[9] The difference between a thermoscope and a thermometer is that the latter has a scale.[10] Though Galileo is often said to be the inventor of the thermometer, there is no surviving document that he actually produced any such instrument.

The first clear diagram of a thermoscope was published in 1617 by Giuseppe Biancani (1566 – 1624): the first showing a scale and thus constituting a thermometer was Santorio Santorio in 1625.[3] This was a vertical tube, closed by a bulb of air at the top, with the lower end opening into a vessel of water. The water level in the tube is controlled by the expansion and contraction of the air, so it is what we would now call an air thermometer.[11]

The word thermometer (in its French form) first appeared in 1624 in La Récréation Mathématique by J. Leurechon, who describes one with a scale of 8 degrees.[12] The word comes from the Greek words θερμός, thermos, meaning "hot" and μέτρον, metron, meaning "measure".

The above instruments suffered from the disadvantage that they were also barometers, i.e. sensitive to air pressure. In 1629, Joseph Solomon Delmedigo, a student of Galileo and Santorio in Padua, published what is apparently the first description and illustration of a sealed liquid-in-glass thermometer. It is described as having a bulb at the bottom of a sealed tube partially filled with brandy. The tube had a numbered scale. Delmedigo did not claim to have invented this instrument. Nor did he name anyone else as its inventor.[13] In about 1654, Ferdinando II de' Medici, Grand Duke of Tuscany (1610–1670) did produce such an instrument, the first modern-style thermometer, dependent on the expansion of a liquid and independent of air pressure.[12] Many other scientists experimented with various liquids and designs of thermometer.

However, each inventor and each thermometer was unique — there was no standard scale. In 1665, Christiaan Huygens (1629–1695) suggested using the melting and boiling points of water as standards and, in 1694, Carlo Renaldini (1615–1698) proposed using them as fixed points on a universal scale. In 1701, Isaac Newton (1642–1726/27) proposed a scale of 12 degrees between the melting point of ice and body temperature.

Era of precision thermometry[edit]

See also: Precision thermometry, Fahrenheit scale, Celsius scale, Mercury-in-glass thermometer (mercury thermometer), Medical thermometer, Clinical thermometer, Pyrometer, and Infrared thermometer

A medical mercury-in-glass maximum thermometer.

In 1714, Dutch[7] scientist and inventor Daniel Gabriel Fahrenheit invented the first reliable thermometer, using mercury instead of alcohol and water mixtures. In 1724, he proposed a temperature scale which now (slightly adjusted) bears his name. He could do this because he manufactured thermometers, using mercury (which has a high coefficient of expansion) for the first time, and the quality of his production could provide a finer scale and greater reproducibility, leading to its general adoption. In 1742, Anders Celsius (1701–1744) proposed a scale with zero at the boiling point and 100 degrees at the freezing point of water,[17] though the scale which now bears his name has them the other way around.[18] French entomologist René Antoine Ferchault de Réaumur invented an alcohol thermometer and, temperature scale in 1730, that ultimately proved to be less reliable than Fahrenheit's mercury thermometer.

The first physician to use thermometer measurements in clinical practice was Herman Boerhaave (1668–1738).[19] In 1866, Sir Thomas Clifford Allbutt (1836–1925) invented a clinical thermometer that produced a body temperature reading in five minutes as opposed to twenty.[20] In 1999, Dr. Francesco Pompei of the Exergen Corporation introduced the world's first temporal artery thermometer, a non-invasive temperature sensor which scans the forehead in about two seconds and provides a medically accurate body temperature.[21][22]


Traditional thermometers were all non-registering thermometers. That is, the thermometer did not hold the temperature reading after it was moved to a place with a different temperature. Determining the temperature of a pot of hot liquid required the user to leave the thermometer in the hot liquid until after reading it. If the non-registering thermometer was removed from the hot liquid, then the temperature indicated on the thermometer would immediately begin changing to reflect the temperature of its new conditions (in this case, the air temperature). Registering thermometers are designed to hold the temperature indefinitely, so that the thermometer can be removed and read at a later time or in a more convenient place. Mechanical registering thermometers hold either the highest or lowest temperature recorded, until manually re-set, e.g., by shaking down a mercury-in-glass thermometer, or until an even more extreme temperature is experienced. Electronic registering thermometers may be designed to remember the highest or lowest temperature, or to remember whatever temperature was present at a specified point in time.

Thermometers increasingly use electronic means to provide a digital display or input to a computer.

Physical principles of thermometry[edit]

Various thermometers from the 19th century.
Comparison of the Celsius and Fahrenheit scales

Thermometers may be described as empirical or absolute. Absolute thermometers are calibrated numerically by the thermodynamic absolute temperature scale. Empirical thermometers are not in general necessarily in exact agreement with absolute thermometers as to their numerical scale readings, but to qualify as thermometers at all they must agree with absolute thermometers and with each other in the following way: given any two bodies isolated in their separate respective thermodynamic equilibrium states, all thermometers agree as to which of the two has the higher temperature, or that the two have equal temperatures.[23] For any two empirical thermometers, this does not require that the relation between their numerical scale readings be linear, but it does require that relation to be strictly monotonic.[24] This is a fundamental character of temperature and thermometers.[25][26][27]

As it is customarily stated in textbooks, taken alone, the so-called "zeroth law of thermodynamics" fails to deliver this information, but the statement of the zeroth law of thermodynamics by James Serrin in 1977, though rather mathematically abstract, is more informative for thermometry: "Zeroth Law – There exists a topological line M which serves as a coordinate manifold of material behaviour. The points L of the manifold M are called 'hotness levels', and M is called the 'universal hotness manifold'."[28] To this information there needs to be added a sense of greater hotness; this sense can be had, independently of calorimetry, of thermodynamics, and of properties of particular materials, from Wien's displacement law of thermal radiation: the temperature of a bath of thermal radiation is proportional, by a universal constant, to the frequency of the maximum of its frequency spectrum; this frequency is always positive, but can have values that tend to zero. Another way of identifying hotter as opposed to colder conditions is supplied by Planck's principle, that when a process of isochoric adiabatic work is the sole means of change of internal energy of a closed system, the final state of the system is never colder than the initial state; except for phase changes with latent heat, it is hotter than the initial state.[29][30][31]

There are several principles on which empirical thermometers are built, as listed in the section of this article entitled "Primary and secondary thermometers". Several such principles are essentially based on the constitutive relation between the state of a suitably selected particular material and its temperature. Only some materials are suitable for this purpose, and they may be considered as "thermometric materials". Radiometric thermometry, in contrast, can be only slightly dependent on the constitutive relations of materials. In a sense then, radiometric thermometry might be thought of as "universal". This is because it rests mainly on a universality character of thermodynamic equilibrium, that it has the universal property of producing blackbody radiation.

Thermometric materials[edit]

Bi-metallic stem thermometers used to measure the temperature of steamed milk
Bi-metallic thermometer for cooking and baking in an oven

There are various kinds of empirical thermometer based on material properties.

Many empirical thermometers rely on the constitutive relation between pressure, volume and temperature of their thermometric material. For example, mercury expands when heated.

If it is used for its relation between pressure and volume and temperature, a thermometric material must have three properties:

(1) Its heating and cooling must be rapid. That is to say, when a quantity of heat enters or leaves a body of the material, the material must expand or contract to its final volume or reach its final pressure and must reach its final temperature with practically no delay; some of the heat that enters can be considered to change the volume of the body at constant temperature, and is called the latent heat of expansion at constant temperature; and the rest of it can be considered to change the temperature of the body at constant volume, and is called the specific heat at constant volume. Some materials do not have this property, and take some time to distribute the heat between temperature and volume change.[32]

(2) Its heating and cooling must be reversible. That is to say, the material must be able to be heated and cooled indefinitely often by the same increment and decrement of heat, and still return to its original pressure, volume and temperature every time. Some plastics do not have this property;[33]

(3) Its heating and cooling must be monotonic.[24][34] That is to say, throughout the range of temperatures for which it is intended to work,

(a) at a given fixed pressure,
either (i) the volume increases when the temperature increases, or else (ii) the volume decreases when the temperature increases;
but not (i) for some temperatures and (ii) for others; or
(b) at a given fixed volume,
either (i) the pressure increases when the temperature increases, or else (ii) the pressure decreases when the temperature increases;
but not (i) for some temperatures and (ii) for others.

At temperatures around about 4 °C, water does not have the property (3), and is said to behave anomalously in this respect; thus water cannot be used as a material for this kind of thermometry for temperature ranges near 4 °C.[26][35][36][37][38]

Gases, on the other hand, all have the properties (1), (2), and (3)(a)(α) and (3)(b)(α). Consequently, they are suitable thermometric materials, and that is why they were important in the development of thermometry.[39]

Constant volume thermometry[edit]

According to Preston (1894/1904), Regnault found constant pressure air thermometers unsatisfactory, because they needed troublesome corrections. He therefore built a constant volume air thermometer.[40] Constant volume thermometers do not provide a way to avoid the problem of anomalous behaviour like that of water at approximately 4 °C.[38]

Radiometric thermometry[edit]

Planck's law very accurately quantitatively describes the power spectral density of electromagnetic radiation, inside a rigid walled cavity in a body made of material that is completely opaque and poorly reflective, when it has reached thermodynamic equilibrium, as a function of absolute thermodynamic temperature alone. A small enough hole in the wall of the cavity emits near enough blackbody radiation of which the spectral radiance can be precisely measured. The walls of the cavity, provided they are completely opaque and poorly reflective, can be of any material indifferently. This provides a well-reproducible absolute thermometer over a very wide range of temperatures, able to measure the absolute temperature of a body inside the cavity.

Primary and secondary thermometers[edit]

A thermometer is called primary or secondary based on how the raw physical quantity it measures is mapped to a temperature. As summarized by Kauppinen et al., "For primary thermometers the measured property of matter is known so well that temperature can be calculated without any unknown quantities. Examples of these are thermometers based on the equation of state of a gas, on the velocity of sound in a gas, on the thermal noisevoltage or current of an electrical resistor, and on the angular anisotropy of gamma ray emission of certain radioactivenuclei in a magnetic field."[41]

In contrast, "Secondary thermometers are most widely used because of their convenience. Also, they are often much more sensitive than primary ones. For secondary thermometers knowledge of the measured property is not sufficient to allow direct calculation of temperature. They have to be calibrated against a primary thermometer at least at one temperature or at a number of fixed temperatures. Such fixed points, for example, triple points and superconducting transitions, occur reproducibly at the same temperature."[41]


Thermometers can be calibrated either by comparing them with other calibrated thermometers or by checking them against known fixed points on the temperature scale. The best known of these fixed points are the melting and boiling points of pure water. (Note that the boiling point of water varies with pressure, so this must be controlled.)

The traditional way of putting a scale on a liquid-in-glass or liquid-in-metal thermometer was in three stages:

  1. Immerse the sensing portion in a stirred mixture of pure ice and water at atmospheric pressure and mark the point indicated when it had come to thermal equilibrium.
  2. Immerse the sensing portion in a steam bath at Standard atmospheric pressure and again mark the point indicated.
  3. Divide the distance between these marks into equal portions according to the temperature scale being used.

Other fixed points used in the past are the body temperature (of a healthy adult male) which was originally used by Fahrenheit as his upper fixed point (96 °F (35.6 °C) to be a number divisible by 12) and the lowest temperature given by a mixture of salt and ice, which was originally the definition of 0 °F (−17.8 °C).[42] (This is an example of a Frigorific mixture.) As body temperature varies, the Fahrenheit scale was later changed to use an upper fixed point of boiling water at 212 °F (100 °C).[43]

These have now been replaced by the defining points in the International Temperature Scale of 1990, though in practice the melting point of water is more commonly used than its triple point, the latter being more difficult to manage and thus restricted to critical standard measurement. Nowadays manufacturers will often use a thermostat bath or solid block where the temperature is held constant relative to a calibrated thermometer. Other thermometers to be calibrated are put into the same bath or block and allowed to come to equilibrium, then the scale marked, or any deviation from the instrument scale recorded.[44] For many modern devices calibration will be stating some value to be used in processing an electronic signal to convert it to a temperature.

Precision, accuracy, and reproducibility[edit]

The "Boyce MotoMeter" radiator cap on a 1913 Car-Nationautomobile, used to measure temperature of vapor in 1910s and 1920s cars.

The precision or resolution of a thermometer is simply to what fraction of a degree it is possible to make a reading. For high temperature work it may only be possible to measure to the nearest 10 °C or more. Clinical thermometers and many electronic thermometers are usually readable to 0.1 °C. Special instruments can give readings to one thousandth of a degree.[citation needed] However, this precision does not mean the reading is true or accurate, it only means that very small changes can be observed.

A thermometer calibrated to a known fixed point is accurate (i.e. gives a true reading) at that point. Most thermometers are originally calibrated to a constant-volume gas thermometer.[citation needed] In between fixed calibration points, interpolation is used, usually linear.[44] This may give significant differences between different types of thermometer at points far away from the fixed points. For example, the expansion of mercury in a glass thermometer is slightly different from the change in resistance of a platinum resistance thermometer, so these two will disagree slightly at around 50 °C.[45] There may be other causes due to imperfections in the instrument, e.g. in a liquid-in-glass thermometer if the capillary tube varies in diameter.[45]

For many purposes reproducibility is important. That is, does the same thermometer give the same reading for the same temperature (or do replacement or multiple thermometers give the same reading)? Reproducible temperature measurement means that comparisons are valid in scientific experiments and industrial processes are consistent. Thus if the same type of thermometer is calibrated in the same way its readings will be valid even if it is slightly inaccurate compared to the absolute scale.

An example of a reference thermometer used to check others to industrial standards would be a platinum resistance thermometer with a digital display to 0.1 °C (its precision) which has been calibrated at 5 points against national standards (−18, 0, 40, 70, 100 °C) and which is certified to an accuracy of ±0.2 °C.[46]

According to British Standards, correctly calibrated, used and maintained liquid-in-glass thermometers can achieve a measurement uncertainty of ±0.01 °C in the range 0 to 100 °C, and a larger uncertainty outside this range: ±0.05 °C up to 200 or down to −40 °C, ±0.2 °C up to 450 or down to −80 °C.[47]

Indirect methods of temperature measurement[edit]

Thermal expansion
Utilizing the property of thermal expansion of various phases of matter.
Pairs of solid metals with different expansion coefficients can be used for bi-metal mechanical thermometers. Another design using this principle is Breguet's thermometer.
Some liquids possess relatively high expansion coefficients over a useful temperature ranges thus forming the basis for an alcohol or mercury thermometer. Alternative designs using this principle are the reversing thermometer and Beckmann differential thermometer.
As with liquids, gases can also be used to form a gas thermometer.
Vapour pressure thermometer
Galileo thermometer[48]
Some compounds exhibit thermochromism at distinct temperature changes. Thus by tuning the phase transition temperatures for a series of substances the temperature can be quantified in discrete increments, a form of digitization. This is the basis for a liquid crystal thermometer.
Band edge thermometry (BET)
Band edge thermometry (BET) takes advantage of the temperature-dependence of the band gap of semiconductor materials to provide very precise optical (i.e. non-contact) temperature measurements.[49] BET systems require a specialized optical system, as well as custom data analysis software.[50][51]
Blackbody radiation
All objects above absolute zero emit blackbody radiation for which the spectra is directly proportional to the temperature. This property is the basis for a pyrometer or infrared thermometer and thermography. It has the advantage of remote temperature sensing; it does not require contact or even close proximity unlike most thermometers. At higher temperatures, blackbody radiation becomes visible and is described by the colour temperature. For example a glowing heating element or an approximation of a star's surface temperature.
Phosphor thermometry
Optical absorbance spectra
Fiber optical thermometer
Electrical resistance
Resistance thermometer which use materials such as Balco alloy
Coulomb blockade thermometer
Electrical potential
Thermocouples are useful over a wide temperature ranges from cryogenic temperatures to over 1000°C, but typically have an error of ±0.5-1.5°C.
Silicon bandgap temperature sensors are commonly found packaged in integrated circuits with accompanying ADC and interface such as I2C. Typically they are specified to work within about —50 to 150°C with accuracies in the ±0.25 to 1°C range but can be improved by binning.[52][53]
Electrical resonance
Quartz thermometer
Nuclear magnetic resonance
Chemical shift is temperature dependent. This property is used to calibrate the thermostat of NMR probes, usually using methanol or ethylene glycol.[54][55] This can potentially be problematic for internal standards which are usually assumed to have a defined chemical shift (e.g 0 ppm for TMS) but in fact exhibit a temperature dependence.[56]
Magnetic susceptibility

See also: Paramagnetism § Curie's law

Above the Curie temperature, the magnetic susceptibility of a paramagnetic material exhibits an inverse temperature dependence. This phenomenon is the basis of a magnetic cryometer.[57][58]


See also: List of temperature sensors

Thermometers utilize a range of physical effects to measure temperature. Temperature sensors are used in a wide variety of scientific and engineering applications, especially measurement systems. Temperature systems are primarily either electrical or mechanical, occasionally inseparable from the system which they control (as in the case of a mercury-in-glass thermometer). Thermometers are used in roadways in cold weather climates to help determine if icing conditions exist. Indoors, thermistors are used in climate control systems such as air conditioners, freezers, heaters, refrigerators, and water heaters.[59] Galileo thermometers are used to measure indoor air temperature, due to their limited measurement range.

Such liquid crystal thermometers (which use thermochromic liquid crystals) are also used in mood rings and used to measure the temperature of water in fish tanks.

Fiber Bragg grating temperature sensors are used in nuclear power facilities to monitor reactor core temperatures and avoid the possibility of nuclear meltdowns.[60]


Nanothermometry is an emergent research field dealing with the knowledge of temperature in the sub-micrometric scale. Conventional thermometers cannot measure the temperature of an object which is smaller than a micrometre, and new methods and materials have to be used. Nanothermometry is used in such cases. Nanothermometers are classified as luminescent thermometers (if they use light to measure temperature) and non-luminescent thermometers (systems where thermometric properties are not directly related to luminescence).[61]


Main article: cryometer

Thermometers used specifically for low temperatures.


Main article: Medical thermometer

Various thermometric techniques have been used throughout history such as the Galileo thermometer to thermal imaging.[48]Medical thermometers such as mercury-in-glass thermometers, infrared thermometers, pill thermometers, and liquid crystal thermometers are used in health care settings to determine if individuals have a fever or are hypothermic.

Food and food safety[edit]

Thermometers are important in food safety, where food at temperatures within 41 and 135 °F (5 and 57 °C) can be prone to potentially harmful levels of bacterial growth after several hours which could lead to foodborne illness. This includes monitoring refrigeration temperatures and maintaining temperatures in foods being served under heat lamps or hot water baths.[59] Cooking thermometers are important for determining if a food is properly cooked. In particular meat thermometers are used to aid in cooking meat to a safe internal temperature while preventing over cooking. They are commonly found using either a bimetallic coil, or a thermocouple or thermistor with a digital readout. Candy thermometers are used to aid in achieving a specific water content in a sugar solution based on its boiling temperature.


Alcohol thermometers, infrared thermometers, mercury-in-glass thermometers, recording thermometers, thermistors, and Six's thermometers are used in meteorology and climatology in various levels of the atmosphere and oceans. Aircraft use thermometers and hygrometers to determine if atmospheric icing conditions exist along their flight path. These measurements are used to initialize weather forecast models. Thermometers are used in roadways in cold weather climates to help determine if icing conditions exist and indoors in climate control systems.

See also[edit]


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  2. ^ abcBolton, Henry Carrington: Evolution of the Thermometer, 1592–1743. (Easton, PA: Chemical Publishing Company, 1900)
  3. ^ abcBigotti, Fabrizio (2018). "The Weight of the Air: Santorio's Thermometers and the Early History of Medical Quantification Reconsidered". Journal of Early Modern Studies. 7 (1): 73–103. doi:10.5840/jems2018714. ISSN 2285-6382. PMC 6407691. PMID 30854347.
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Further reading[edit]

  • Middleton, W.E.K. (1966). A history of the thermometer and its use in meteorology. Baltimore: Johns Hopkins Press. Reprinted ed. 2002, ISBN 0-8018-7153-0.
  • History of the Thermometer
  • [1] - Recent review on Thermometry at the Nanoscale

External links[edit]

Look up thermometer in Wiktionary, the free dictionary.
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