How do thermometers work?

It depends on the type of thermometer. Digital thermometers with a metal probe are based on the fact that resistance of the metal part (how hard it is for electricity to flow through it) changes as the temperature changes, such as when it is inserted under the tongue. The thermometer has a microchip that measures how much resistance there is and then translates that into temperature. Other “thermometers work by using heat or infrared sensors to measure the temperature at a specific part of the body,” Dr. Katz explains.

What type of thermometer is most accurate?

Dr. Katz says that digital rectal thermometers are the most accurate at measuring core temperature. That’s because they measure the internal body temperature by insertion, and the reading is less likely to be influenced by external factors, such as drinking hot or cold beverages and environmental temperatures.

Do forehead thermometers actually work?

While forehead thermometers are popular (because they don’t require physical contact to read temperature), research studies have found that their accuracy may be lower compared to ear or armpit thermometers, especially if not positioned correctly, says Dr. Katz. Positioning is important to get a correct reading because different areas of the body have varying levels of heat concentration. “Forehead thermometers should be held perpendicularly to the person’s forehead at the distance recommended by the manufacturer of the thermometer for optimal accuracy,” he explains. Temperatures should also be taken away from direct sunlight, a heat source, and without a hat or headband, to minimize factors that can influence the temperature reading.

How do you clean your thermometer?

A thermometer should be cleaned after each use. Dr. Katz recommends washing the tip of the thermometer with cold water and antibacterial liquid soap, which should not come into contact with the screen. You can also wipe down the tip with alcohol-based wipes of at least 70% alcohol to sterilize the tip, he adds. Make sure to wipe the thermometer dry with a soft cloth after each clean.

Can an adult use a baby thermometer?

Most baby thermometers can be used by adults. Some baby thermometers have been designed with babies in mind, meaning they may be smaller and have a flexible tip. If using a baby thermometer , use as instructed. The reading of an adult’s temperature should still be accurate on a baby thermometer.

The 6 Best Thermometers of 2022

We independently research, test, review, and recommend the best products. Healthcare professionals review articles for medical accuracy. Learn more about our process. If you buy something through our links, we may earn a commission.

Best thermometer test — Verywell Health / Leticia Almeida

While your body temperature fluctuates throughout the day due to a variety of factors—activity, time of day, and even what you're eating—a sudden temperature change can be an indicator that it might be time to see a doctor.

Tested & Approved

The Kinsa Smart Thermometer is a great pick for anyone looking for an effective oral thermometer that allows you to track your body temperature. When you have a fever and want the most precise reading, we recommend Vick’s Speedread Digital Thermometer.

While historically, 98.6 degrees Fahrenheit has been considered “normal” body temperature, one recent study calculated it is closer to 97.9. Regardless, health experts are pretty unanimous when it comes to what defines a fever—100.4 degrees Fahrenheit. “Fever is often just a sign of the body fighting some type of an infection—and an elevated temperature is a good thing and is helping your body recover,” explains Maryellen Flaherty-Hewitt, MD, FAAP, Interim Section Chief of General Pediatrics Yale Medicine.

Identifying a fever is crucial and “accuracy is critical for your physician to make an appropriate assessment of the situation,” she continues. She adds that investing in an accurate thermometer can keep you and your family’s health in check. When shopping for a thermometer, keep the user in mind as well as the type of thermometer the user will be comfortable with. Additional thermometer features, like connected apps, can also be beneficial in tracking your health. To make shopping easier, we tested 25 thermometers and reviewed each one to find the best based on five categories: ease of setup, response time, consistency of results, ease of use, and data readability.

Here are the best thermometers on the market today.

Our Top Picks

Best Overall:

Kinsa Smart Thermometer at Amazon

Jump to Review

Best Budget:

iProven Dt-R1221AWG Medical Thermometer at Amazon

Jump to Review

Best Multi-Use:

Chooseen Infrared Thermometer at Amazon

Jump to Review

Best Ear Thermometer:

Braun ThermoScan 5 IRT6500 at Amazon

Jump to Review

Best Forehead:

iHealth No Touch Forehead Thermometer at Amazon

Jump to Review

Best Fever Indicator:

Vicks Speedread Thermometer at Walmart

Jump to Review

In This Article

Our Picks
How We Tested
What to Look For
Why Trust Verywell Health

4.9

Courtesy of Amazon

Our Ratings

Setup

4.5/5
Responsiveness

4.9/5
Consistency

4.8/5
Ease of Use

5/5
Data Readability

5/5

Pros

Quick results
For underarm, oral, and rectal use
Tracks your health status

Cons

May require more time for setup

The Kinsa Smart Thermometer was our favorite overall pick and received no less than a five across some of the most important attributes: response time, ease of use, data readability, and durability, making it the best overall. This smart thermometer is super efficient and gives your temperature reading within eight seconds. The tip is flexible, making it ideal to take temperatures from your mouth, under the arm, or rectal area. Plus, it syncs to the free Kinsa app to record your health data and provide personalized guidance based on your temperature and symptoms.

Our product testers noted that because the thermometer connects to an app via Bluetooth, setup may take longer than other thermometers, scoring a four out of five in the ease of setup category, Regardless, this thermometer received an overall score of five.

Weight (Manufacturer Stated): 1.59 ounces | Bluetooth/App Connectivity: Yes | Dimensions (Manufacturer Stated): 5.7 x 3 x 1 inches | Power Source: Batteries required

4.5

Courtesy of Amazon

Our Ratings

Setup

5/5
Responsiveness

3.5/5
Consistency

3.8/5
Ease of Use

5/5
Data Readability

4/5

Pros

Displays results in easy-to-read format
Budget-friendly
Comes with a case

Cons

10-second response time
Not recommended for axillary temperature measurement

The iProven Oral and Rectal Thermometer is reliable and won’t put a dent in your wallet, and that’s why we love it as our best budget choice. It’s the most financially-friendly option on the list, and we liked how easy it was to use and clean. Once the temperature is displayed on the screen, the arrow points to three different faces: smiley face, frowny face, or a straight line mouth face, making the results easy to understand and kid-friendly. Plus, it comes with a case, which stayed intact and protected the thermometer when our testers dropped it.

The thermometer received four and five ratings for most attributes, except response time. Our tester noted that the response time took roughly 10 seconds. While not the fastest, it delivers information quickly.

Weight (Manufacturer Stated): 1.45 ounces | Bluetooth/App Connectivity: No | Dimensions (Manufacturer Stated): 5.12 x 0.79 x 0.43 inches | Power Source: Batteries required

iProven Oral Thermometer — Verywell Health / Leticia Almeida

4.4

Walmart

Our Ratings

Setup

5/5
Responsiveness

4.5/5
Consistency

3.5/5
Ease of Use

4/5
Data Readability

5/5

Pros

Easy setup
Quick results
Displays results in easy-to-read format

Cons

Doesn’t come with a sanitary cap

Using an infrared temperature sensor, the Chooseen thermometer can read your temperature from your forehead without ever coming into physical contact, making it the best multi-use and hygienic option. It can also function as an ear thermometer for those who don’t want to put a device in their mouth or rectum. After scanning your body, the results are delivered within a second to a large LCD screen that makes reading results easy. Bonus: The temperatures are highlighted in three colors to signal your health status: green for normal, orange for light fever, and red for high fever.

It’s also built with a one-button design that is suitable for adults and kids. You can use the thermometer to get the temperature of different household items, too. It can take a couple of tries to lock in the perfect position for the thermometer to grab your temperature, per our tester, but it’s generally easy to use.

Weight (Manufacturer Stated): 4.66 ounces | Bluetooth/App Connectivity: No | Dimensions (Manufacturer Stated): 6.69 x 1.93 x 1.85 inches | Power Source: Batteries required

Chooseen Digital Ear Thermometer — Verywell Health / Leticia Almeida

Courtesy of BuyBuyBaby

Our Ratings

Setup

5/5
Responsiveness

4.5/5
Consistency

4.8/5
Ease of Use

5/5
Data Readability

4.2/5

Pros

Uses infrared technology to get accurate reading
Pre-warmed tip
Easy to use

Cons

Expensive

Using infrared technology, the Braun thermometer measures heat generated by your eardrum to determine the body’s temperature. It flashes a light and beeps to let you know that the device is properly positioned. It’s built with a pre-warmed tip to minimize a cooling effect and the age precise technology delivers a reading based on your age, making this ideal for ear use on people of all ages. We found the thermometer to be easy to use.

One caveat is that it’s got a heftier price tag than all the thermometers on the list. But with all of the unique features, we think it’s worth the splurge.

Weight (Manufacturer Stated): 10.4 ounces | Bluetooth/App Connectivity: No | Dimensions (Manufacturer Stated): 5.4 x 2.7 x 8.2 inches | Power Source: Batteries required

Braun Digital Ear Thermometer — Verywell Health / Leticia Almeida

4.2

Courtesy of Amazon.

Our Ratings

Setup

4/5
Responsiveness

5/5
Consistency

4/5
Ease of Use

3.5/5
Data Readability

4.5/5

Pros

Fast results
Large LED screen
Vibration alert

Cons

Tricky to use at the start

Getting your temperature reading near the face can be a tricky endeavor, but thankfully, the iHealth thermometer uses some neat technology. Using infrared sensors and data points that scan your forehead, the thermometer can read your temperature without ever touching you, making it the best for the forehead. Not only is the thermometer hygienic, but it also delivers lightning-fast results. Our tester noted that the response time was almost instant. The thermometer has a single button and a large LED screen, which is best suited for people of all age groups who want a simple device.

This thermometer received no lower than a four for all categories except ease of setup, which received a three. Our tester noted that they didn’t know what to press or how long to push the button to turn it on, but was able to figure it out shortly after. Nonetheless, this thermometer features a sleek, simple design that offers instantaneous results.

Weight (Manufacturer Stated): 3.17 ounces | Bluetooth/App Connectivity: No | Dimensions (Manufacturer Stated): 1.54 x 1.34 x 5.39 inches | Power Source: Batteries required

4.6

Courtesy of Vicks

Our Ratings

Setup

5/5
Responsiveness

4.3/5
Consistency

4.5/5
Ease of Use

5/5
Data Readability

4.5/5

Pros

Color coded fever indicator
Waterproof
Affordable

Cons

Longer response time

It’s important to have a thermometer handy when you feel a fever coming on, and this one from Vicks is best for detecting fevers. It uses a color-coded fever system to detect any increases in body temperature. If you have a fever, the screen will illuminate red to signal a high temperature (over 100.4 F). The screen will turn green if you have a normal temperature, or yellow if you have an elevated temperature.

One thing our tester noted is that response time is a little slower than other thermometers on the list, taking about eight to nine seconds to give a reading. If you don’t mind waiting a few more seconds for your reading, then this thermometer may be for you. Even more impressive? It’s waterproof, comes with a storage case, and has a one-year warranty in case anything happens to it.

Weight (Manufacturer Stated): 1.6 ounces | Bluetooth/App Connectivity: No | Dimensions (Manufacturer Stated): 3.1 x 1.2 x 7.5 inches | Power Source: Batteries required

Vicks Speedread Digital Thermometer — Verywell Health / Leticia Almeida

		Overall Rating	Setup	Responsiveness	Consistency	Ease of Use	Data Readability
Best Overall: Kinsa Smart Thermometer	Amazon	4.9	4.5	4.9	4.8	5	5
Best Budget: iProven Dt-R1221AWG Medical Thermometer	Amazon	4.5	5	3.5	3.8	5	4
Best Multi-Use: Chooseen Infrared Thermometer	Amazon	4.4	5	4.5	3.5	4	5
Best Ear Thermometer: Braun ThermoScan 5 IRT6500	Amazon	4	5	4.5	4.8	5	4.2
Best Forehead: iHealth No Touch Forehead Thermometer	Amazon	4.2	4	5	4	3.5	4.5
Best Fever Indicator: Vicks Speedread Thermometer	Walmart	4.6	5	4.3	4.5	5	4.5

Final Verdict

Because the Kinsa Quickcare Thermometer is easy to use, delivers accurate results, and provides personalized guidance based on your body temperature, we named it the best overall. If you’re looking for a thermometer specially designed for a fever, the Vick’s Speedread Digital Thermometer is another great option. It’s built with a color-coded system to monitor any increases in temperature.

How We Rated

4.8 to 5 stars: These are the best thermometers we tested. We recommend them without reservation.

4.5 to 4.7 stars: These thermometers are excellent—they might have minor flaws, but we still recommend them.

4.0 to 4.5 stars: We think these are great thermometers, but others are better.

3.5 to 3.9 stars: These thermometers are just average.

3.4 and below: We don't recommend thermometers with this rating; you won't find any on our list.

How We Tested

The Verywell Health team spent eight hours at the Verywell Testing Lab and several weeks at home, testing 25 thermometers to find the best ones. The four testers, consisting of three adults and one child tester, compared the thermometers using the following qualities: ease of setup, response time, consistency of results, ease of use, and data readability.

Best thermometers test — Verywell Health / Leticia Almeida

For example, testers looked for how easy it was to set up the product from the box, how long it took for each thermometer to deliver a temperature reading, and additional features, such as a color-coded fever indicator and app connectivity. This process was repeated for each thermometer. Thermometers that took too long to deliver results or didn’t function properly were excluded from the roundup.

Additionally, overall value ratings were given by our testers, while star ratings were based on the average of all attribute scores. None of our picks received perfect five-star ratings across the board and all scales had something that could have been improved.

A Note About Accuracy

Because temperature can fluctuate throughout the day, we decided we did not have the resources to give a valid accuracy rating. Because of this, we focused on using the selected attributes to determine whether or not they would make our list.

What to Look for in a Thermometer

Types

There are different types of thermometers that target different areas of the body to get your temperature readings, such as oral, tympanic, temporal, and rectal areas. According to Bradley Katz, MD, PhD, professor at the University of Utah Medical Center and CEO of Axon Optics, rectal thermometers are considered to be the most accurate because they check internal body temperature and are less likely to be influenced by drinking cold or hot drinks, or fluctuating temperatures. However, in practice, oral thermometers are used among adults. Rectal thermometers are more widely used among children or patients in a hospital setting, Dr. Katz adds.

Oral - thermometers that read temperature from the mouth
Tympanic - thermometers that read temperature from the ear
Temporal - thermometers that read temperature from the forehead
Rectal - thermometers that read temperature from the anus or anal canal
Axillary - thermometers that read temperature from the armpit

Additional Features

When looking for a thermometer, Dr. Katz recommends people look for a thermometer that’s easy to read and use. You will “also want thermometers that can give accurate readings in the shortest time possible for the convenience,” Dr. Katz says. “If you’re buying a thermometer for your baby or infant, a baby thermometer is more suitable as they have flexible tips and smaller size.”

Beyond the temperature reading capabilities, some thermometers have additional features, such as a color-coded system that informs you whether you have a fever or high temperature. Some smart thermometers come with a free, downloadable app that keeps a record of your temperatures and provides health insights.

Type of User

There are different types of thermometers that are better suited for various ages. For example, baby thermometers tend to be smaller in size and have a flexible tip. Others are specialized for specific uses, such as fever. Ultimately, the thermometer you choose will depend on your age and what you need it for.

Frequently Asked Questions

How do thermometers work?

It depends on the type of thermometer. Digital thermometers with a metal probe are based on the fact that resistance of the metal part (how hard it is for electricity to flow through it) changes as the temperature changes, such as when it is inserted under the tongue. The thermometer has a microchip that measures how much resistance there is and then translates that into temperature.
Other “thermometers work by using heat or infrared sensors to measure the temperature at a specific part of the body,” Dr. Katz explains.
What type of thermometer is most accurate?

Dr. Katz says that digital rectal thermometers are the most accurate at measuring core temperature. That’s because they measure the internal body temperature by insertion, and the reading is less likely to be influenced by external factors, such as drinking hot or cold beverages and environmental temperatures.
Do forehead thermometers actually work?

While forehead thermometers are popular (because they don’t require physical contact to read temperature), research studies have found that their accuracy may be lower compared to ear or armpit thermometers, especially if not positioned correctly, says Dr. Katz.
Positioning is important to get a correct reading because different areas of the body have varying levels of heat concentration. “Forehead thermometers should be held perpendicularly to the person’s forehead at the distance recommended by the manufacturer of the thermometer for optimal accuracy,” he explains. Temperatures should also be taken away from direct sunlight, a heat source, and without a hat or headband, to minimize factors that can influence the temperature reading.
How do you clean your thermometer?

A thermometer should be cleaned after each use. Dr. Katz recommends washing the tip of the thermometer with cold water and antibacterial liquid soap, which should not come into contact with the screen. You can also wipe down the tip with alcohol-based wipes of at least 70% alcohol to sterilize the tip, he adds. Make sure to wipe the thermometer dry with a soft cloth after each clean.
Can an adult use a baby thermometer?

Most baby thermometers can be used by adults. Some baby thermometers have been designed with babies in mind, meaning they may be smaller and have a flexible tip. If using a baby thermometer, use as instructed. The reading of an adult’s temperature should still be accurate on a baby thermometer.

Why Trust Verywell Health

Receiving her master’s degree in public health in 2020, Kayla Hui is a seasoned public health practitioner and health journalist. She has interviewed dozens of experts, reviewed numerous research studies, and tested a plethora of products to deliver well-researched product reviews and roundups. Her goal is to help readers make more informed decisions about their health and well-being.

The 6 Best Thermometers of 2022, Tested in Our Lab

The Kinsa Smart Thermometer is a vital addition to your at-home first aid kit

Tested & Approved

Best Overall: Kinsa Smart Thermometer

Best Budget: iProven Dt-R1221AWG Medical Thermometer

Best Multi-Use: Chooseen Infrared Thermometer

Best Ear Thermometer: Braun ThermoScan Digital Ear Thermometer

Best Forehead: iHealth No Touch Forehead Thermometer

Best Fever Indicator: Vicks Speedread Thermometer

Compare

Final Verdict

How We Rated

How We Tested

A Note About Accuracy

What to Look for in a Thermometer

Types

Additional Features

Type of User

Frequently Asked Questions

Why Trust Verywell Health