Types of Food Thermometers: Which One to Use

The main types of food thermometer are digital instant-read (thermocouple or thermistor), dial (oven-safe or instant-read), leave-in probes with a cord or wireless link, pop-up timers and single-use indicators. Instant-read digital models are the most versatile. Infrared guns read only surface temperature, so they can't tell you whether meat is cooked.

Key facts

USDA FSIS times thermocouples at 2–5 seconds, thermistors at about 10 seconds and dial instant-reads at 15–20 seconds.
Dial oven-safe thermometers need 2–2½ inches of food and aren't meant for anything under 3 inches thick.
FSIS says most food thermometers are accurate to within 2–4°F.
A calibrated thermometer reads 32°F (0°C) in ice water and 212°F (100°C) in boiling water at sea level.
Infrared thermometers measure only the surface, not the inside of food.

Why the type of thermometer matters

A food thermometer is the only reliable way to know food has reached a safe internal temperature; Penn State Extension notes that color, juices and texture can all mislead. Yet Penn State, citing a 2019 USDA Economic Research Service survey, reports that while 67% of US adults own a food thermometer, only 14% of home cooks use one in a typical week. Pick a type that suits how you cook.

Thermometers differ in three ways that matter in the kitchen: how fast they read, how deep the sensor has to go, and whether they can stay in food while it cooks. The USDA Food Safety and Inspection Service (FSIS) groups them as digital, dial and "other" types.

Type	Reading time	Minimum depth	Stays in during cooking?	Can be calibrated?
Digital thermocouple	2–5 seconds	1/4 inch	No	Yes
Digital thermistor	About 10 seconds	1/2 inch	No	Some models
Dial instant-read	15–20 seconds	2–2½ inches	No	Some models
Dial oven-safe	1–2 minutes	2–2½ inches	Yes	Some models
Oven cord probe	About 10 seconds	1/2 inch	Yes	No
Wireless / smart probe	Continuous	1 inch	Yes	Yes
Thermometer fork	2–10 seconds	1/4 inch	No	No
Single-use indicator	5–10 seconds	About 1/2 inch	No	No
Pop-up timer	Pops at a set temperature	Factory-placed	Yes	No

Digital instant-read thermometers

A digital instant-read thermometer has its sensor in the tip of a thin probe, so it reads thin and thick foods alike. It isn't designed to stay in the oven; you check the food near the end of cooking and take the thermometer out. Penn State Extension notes that digital models run on a battery. FSIS describes two kinds:

Thermocouple

The fastest type. FSIS says a thermocouple gives a reading in 2–5 seconds with as little as 1/4 inch in the food, and its probe is very thin, about 1/16 inch on common models. That makes it easy to check several spots on a roast or the middle of a thin chop. FSIS notes thermocouples can be calibrated but tend to cost more.

Thermistor

A thermistor takes about 10 seconds, needs at least 1/2 inch of depth, and has a probe about 1/8 inch thick. Only some models can be calibrated. University of Maryland Extension calls a digital instant-read thermometer the best choice for home cooks because it works on both thick and thin foods.

Dial thermometers

Dial thermometers use a bimetal coil in the stem that turns a needle as it heats. The sensing area runs along the stem, not just at the tip, so they average the temperature over a longer section and need deeper food.

Oven-safe dial thermometers

An oven-safe dial thermometer goes into a roast, whole bird or casserole at the start and stays there. It takes 1–2 minutes to settle and needs 2–2½ inches of food. FSIS cautions that heat traveling along the metal stem can push the reading falsely high, recommends checking a second or third spot, and says not to use one in food less than 3 inches thick.

Dial instant-read thermometers

These read in 15–20 seconds at 2–2½ inches deep. They suit roasts, casseroles and soups; for a thin food such as a burger, insert the stem sideways. They aren't meant to stay in food during cooking. Maryland Extension notes they need more frequent recalibration and are less precise than digital models.

Probe, leave-in and wireless thermometers

A leave-in probe lets you watch the temperature climb without opening the oven or smoker.

Oven cord probe: a probe on a heat-proof cord connects to a base unit that sits outside the oven and can sound an alert at a set temperature. FSIS notes it reads in about 10 seconds and needs 1/2 inch of depth, but it can't be calibrated.
Wireless or smart probe: the probe stays at least 1 inch into the thickest part of the food and sends live readings by Bluetooth or Wi-Fi to a base unit or a phone app, which can send alerts. FSIS says these work in ovens, grills and slow cookers and can be calibrated, but they cost more.
Thermometer fork: a grilling fork with a sensor in one tine. It reads in 2–10 seconds once the tine is fully inserted at least 1/4 inch, isn't meant to stay in food, and can't be calibrated.

Pop-up timers and single-use indicators

Pop-up timers come in some turkeys and roasting chickens. Inside, a spring-loaded stem is held in place by a material that dissolves at a set temperature, letting the stem pop up. FSIS says they're reliable to within 1–2°F when correctly placed, but they measure only one spot, so FSIS still recommends checking with a regular food thermometer.

Single-use temperature indicators are disposable strips or sticks that change color when they reach a target range, such as 160–170°F. Each is made for a specific temperature, so use it only with the food it's designed for. FSIS says they read in 5–10 seconds at about 1/2 inch deep.

Candy, deep-fry and liquid-filled thermometers

FSIS describes a thermometer that measures about 100–400°F for candy and jelly making and for deep frying in hot oil. Older liquid-filled thermometers (glass or metal stem) need at least 2 inches of depth and aren't suited to thin foods; FSIS warns that glass stems can break in food.

Infrared thermometers and temperature guns

An infrared (IR) thermometer, often called a temperature gun, reads heat radiating from a surface without touching it. Thermometer maker ThermoWorks explains that IR thermometers measure only surface temperature, so they can't show whether the center of a chicken breast or burger is done. Shiny metal also reflects its surroundings and reads falsely low.

IR guns are useful for quick surface checks, such as food on a buffet line. For any safety call on meat, poultry, fish or leftovers, use a probe thermometer that goes into the food.

Oven, fridge and freezer thermometers

Appliance thermometers measure the air in an appliance, not the food. FSIS's "Appliance Thermometers" page says most are liquid-filled or use a bimetal coil:

Oven thermometer: hang it from a rack in the center or set it on a shelf, preheat to 325–350°F, then read it again after 5 minutes because the oven cycles on and off. FSIS suggests testing several settings (325, 350, 375 and 400°F); if the oven is always off by the same amount, adjust your settings.
Fridge thermometer: put it in a glass of water in the middle of the fridge and read it after 5–8 hours. The fridge should stay at 40°F (4°C) or below; see what temperature a refrigerator should be.
Freezer thermometer: set it between frozen packages; aim for 0°F (−18°C).

How to calibrate a food thermometer

FSIS says most food thermometers are accurate to within 2–4°F, and NDSU Extension recommends checking calibration at least once a month and whenever a thermometer is dropped. There are two methods:

Ice water (32°F / 0°C): fill a large glass with ice, add drinking water and stir. Put the stem at least 2 inches in without touching the sides or bottom, wait at least 30 seconds, and read it without removing it. It should show 32°F.
Boiling water (212°F / 100°C at sea level): bring clean water to a boil (FSIS says distilled water is most accurate), insert the stem at least 2 inches, clear of the pan, and wait 30 seconds. It should read 212°F.

Water boils at a lower temperature at altitude; NDSU Extension lowers the target about 1°F for each 550 feet above sea level and suggests the ice method for high elevations. If a dial thermometer reads wrong, turn the calibration nut under the dial while the stem stays in the water. If a digital model can't be adjusted, Penn State Extension says to replace it. Cleaning tips and more calibration detail are in our guide to using a meat thermometer.

Where to insert a food thermometer

For any type, the sensing area goes in the thickest part of the food, away from bone, fat and gristle. Whole poultry is checked in the thigh, wing and breast. Our meat thermometer guide covers placement food by food, and the cooking temperatures hub lists the USDA target for each: for example, turkey and chicken at 165°F, pork chops at 145°F plus a 3-minute rest, and salmon at 145°F.

Questions people ask

What is the most accurate type of food thermometer?

FSIS describes digital thermocouples as the fastest, reading in 2–5 seconds, and they can be calibrated. Any type is only as accurate as its calibration and placement.

Can I use an infrared thermometer to check meat?

No. Infrared thermometers read only the surface temperature, not the inside of the meat. Use a probe that goes into the thickest part.

Can you leave an instant-read thermometer in the oven?

No. FSIS says instant-read models aren't designed to stay in food while it cooks. Use an oven-safe dial thermometer or a leave-in probe instead.

What is one effective way to calibrate a thermometer?

The ice water method: put the stem at least 2 inches into a glass of ice and water for 30 seconds. It should read 32°F; adjust or replace it if not.

Are pop-up turkey timers reliable?

FSIS says they're accurate to within 1–2°F when correctly placed, but they read only one spot. Confirm with a food thermometer.

Types of Food Thermometers: Instant-Read, Probe, Infrared and More