Best Thermometer Buying Guide

Jun 13, 2023

When you or someone you care for gets sick, it’s important to know if a fever has set in—and if so, how high. Running a temperature for more than three days, for example, is a sign that it’s time to talk to your doctor, and temperatures above 104°F can cause seizures in young children. That’s why having a good thermometer that provides accurate readings is key. For babies under 3 months old, temperatures should be taken rectally, and any fever in this age group warrants a call to the doctor.

But with so many types of thermometers on the market—from infrared to digital stick thermometers—it can be difficult to know what kind to choose.

To help you select the best thermometer for your needs, we tested thermometers for accuracy (on a non-feverish adult), repeatability (whether the same temperature was achieved over a few tries), and evaluated features and accessories that improve performance.

Whatever type of thermometer you choose, it should be easy to use and comfortable for you or your child. With this in mind, we tested 10 fever thermometers for accuracy and also quizzed 19 children ages 4 and up about their comfort level with each thermometer.

For Babies Younger Than 3 Years OldThe American Academy of Pediatrics (AAP) recommends taking a rectal temperature in infants and children younger than 3, because it’s most accurate. An armpit temperature can be easier, but it’s the least accurate. If the armpit temperature is above 99°F, double-check by taking a rectal temperature.

For Children 3 and UpIn this age group, taking an oral temperature is OK, but some tots may have trouble keeping the thermometer in their mouths long enough to get an accurate reading. An ear thermometer is another option for older babies and children. It gives quick results, but positioning it correctly can be tricky and you may not get the same temperature in both ears. Temporal artery thermometers, which read the infrared heat waves released by the artery in the temple along the side of the head, are acceptable for babies 3 months and older. But they are only ok as an initial screening device for younger babies—if there’s any sign of fever, re-check it with a rectal thermometer.

For Teenagers and AdultsOral or infrared thermometers can be convenient and give an accurate reading.

New options have replaced the glass thermometers you may have grown up with (and which we recommend replacing; for more, see below). We tested digital stick and infrared thermometers. Other types (not tested) include: digital pacifier thermometers, reusable forehead thermometer strips, and wearable (also called sticker) thermometers for kids.

A digital stick thermometer is the most widely sold and cheapest type. Look for one with an LCD display that’s easy to read and a start button that’s easy to press. Many thermometers have an audible beep or other signal indicating that the reading is complete—meaning you won’t have to keep checking your watch.Digital thermometers rely on batteries to function.

Decide whether you want a rigid-tip or flexible-tip thermometer. Generally, children and adults who had their temperatures taken orally in our tests said that rigid digital stick thermometers were less comfortable than flexible types. Many rigid-tip thermometers are designed to take underarm or rectal temperatures as well as oral temperatures. Not all flexible-tip thermometers can be used rectally, so you’ll need to read the labels.

Where: oral, underarm, and rectal (with the exception of some flexible-tip models, so be sure to read labels).

Infrared thermometers measure the heat emitted by the body. Some infrareds can be difficult to position, but their digital readout takes just 1 to 3 seconds—among the shortest times of all the thermometers we tested. But these thermometers are also among the most expensive—and they aren’t necessarily more accurate than less-costly digital stick thermometers.

Infrared tympanic thermometers measure the temperature inside the ear canal. Note that if an ear thermometer probe tip is cold, it can give you a cooler reading. Some models have a pre-warming feature for better accuracy.This type of thermometer is quick and easy to use. The top infrared thermometers in our tests were forehead models. Not surprisingly, the children in our study preferred forehead-type thermometers to oral and ear types. One young participant expressed a common sentiment among testers of forehead thermometers: "It felt really smooth on my forehead and it glided easily."

A non-contact infrared thermometer typically works by holding the thermometer wand an inch or two from the patient’s forehead and pressing a button to display two red circles of light on the forehead. You then move the thermometer closer to or farther from the forehead until the two red circles converge into one red circle and release the button, at which point the temperature is displayed. If your child is restless, it may be difficult to get an accurate temperature. Many thermometers have an audible beep or other signal indicating that the reading is complete--meaning you won’t have to keep checking your watch. The manufacturer says you can also use this thermometer to measure the temperature of a room or the baby’s bath or bottle, but we did not test those features.

Where: forehead, ear, or non-contact (depending on model)

Glass thermometers wth mercury have largely been replaced by digital versions that don’t contain the potentially dangerous metal. But you may still have an old mercury thermometer or two lurking in a your medicine cabinet. Mercury exposure can cause potentially deadly health problems if the thermometer breaks. So if you’re still holding onto a glass thermometer containing mercury (some glass thermometers contain alcohol), the AAP advises getting rid of it. (You can usually tell if a thermometer contains mercury because the interior fluid is a metallic silver, white, or gray. In the alcohol version, the fluid will be semi-transparent and red.) But don’t just throw a mercury thermometer into the trash. Products containing mercury are considered “hazardous waste.” Seal the item in a plastic bag and check with your local waste district or trash collector about disposing of it correctly. Use the recycling locator on Earth911.com to find a center that handles mercury near you.

Here’s what to consider before you buy.

FeaturesAs simple as digital thermometers are, some have bells and whistles that you might find convenient, such as soft or curved tips, or beeps that tell you when they’re in the right spot or when they’ve finished measuring the temperature. (See below, “Choosing a Thermometer,” for more info.)

Response TimeA readout from a digital stick thermometer may take from 10 seconds to more than 80 seconds, depending on the model. Infrared thermometer readouts take just 1 to 3 seconds, but may not be any more accurate than an inexpensive digital stick thermometer.

SafetySome models come with probe covers, protective case covers, and other accessories that may pose a choking hazard for children. If the model you buy includes small parts, keep them out of the hands of unsupervised children.

ExtrasIf you’re purchasing an inexpensive digital stick thermometer, consider purchasing two: one to take oral temperatures and another to take rectal temperatures. That way you won’t have to worry about keeping disposable thermometer covers on hand. Label each one with permanent marker for its particular use.

Thermometers can come with a range of features. Before you buy, know which features best suit your needs.

For ease-of-use and comfort, some thermometers have soft (flexible) or curved tips. Soft-tip versions can’t be used rectally, so read the packaging carefully

A large, backlit display and large digits can help you to easily read temperatures at night or in low light.

A line or mark showing an end point for insertion can prevent injury to your baby when you’re taking a rectal temperature. Be sure to follow the manufacturer’s instructions carefully when using thermometers rectally. Note that at Consumer Reports, thermometers were not tested rectally.

Some models will have a special beep when a temperature exceeds 99.5 degrees F. Others have visual fever alerts, with the display changing color (green, yellow, red) to indicate temperature level.

Some models record the last temperature taken, so you can determine in which direction your baby’s fever is going. Some also feature an automatic shutoff to preserve battery life.

PHOTO: BRAUN

A temperature that’s a dangerous fever for one age group can be not-so-serious for another. This technology allows you to input the person’s age. A color-coded display tells you if the result is normal, elevated, or high for that age group.

PHOTO: BRAUN

For ease-of-use and comfort, some thermometers have soft (flexible) or curved tips. Soft-tip versions can’t be used rectally, so read the packaging carefully

A large, backlit display and large digits can help you to easily read temperatures at night or in low light.

A line or mark showing an end point for insertion can prevent injury to your baby when you’re taking a rectal temperature. Be sure to follow the manufacturer’s instructions carefully when using thermometers rectally. Note that at Consumer Reports, thermometers were not tested rectally.

Some models will have a special beep when a temperature exceeds 99.5 degrees F. Others have visual fever alerts, with the display changing color (green, yellow, red) to indicate temperature level.

Some models record the last temperature taken, so you can determine in which direction your baby’s fever is going. Some also feature an automatic shutoff to preserve battery life.

PHOTO: BRAUN

A temperature that’s a dangerous fever for one age group can be not-so-serious for another. This technology allows you to input the person’s age. A color-coded display tells you if the result is normal, elevated, or high for that age group.

PHOTO: BRAUN

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