How To Calibrate Food Thermometers (Digital & Analog)

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To cook meat and poultry to perfection, you need an accurate food thermometer. But after years of use, that once-reliable digital or analog thermometer might need to be calibrated. Two or three degrees off makes all the difference between a medium-rare roast and a well-done roast as you can see from our meat temperature guide. If you don’t own a meat thermometer, check out our review of the best ones.

Make sure your thermometer has a reset button

Calibrating a digital meat thermometer is a very easy, two-step process. However, you do need to first see if your thermometer has a calibration reset button, like four of the seven thermometers we tested. If it doesn’t have a reset or other way for calibration (read your thermometer’s instructions, if you still have them), you can still check the thermometer’s accuracy by performing these two tests.

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Ice water test

calibrating a thermometer in iced water

Fill a tall glass with crushed ice and add cold water. Stir the ice and water for three minutes. Insert the thermometer’s probe two inches into the center of glass — try to keep the probe from touching ice — and hold it there for 30 seconds. (An instant-read thermometer will register a temperature in about 10 seconds; a wired probe will take longer.) Your thermometer should read 32 ℉ or 0 ℃. If it doesn’t, push the reset or calibrate button (usually designated on the thermometer as CAL), until it hits 32 ℉ or 0 ℃.

Boiling water test

calibrating a thermometer in boiling water

Bring a saucepan of water to a rolling boil. Insert the thermometer probe into the center of the pot, about two inches into the water. Hold it for 30 seconds (use a pot holder or dish towel to protect your fingers from the hot steam). Your thermometer should register 212 ℉ or 100 ℃. (The boiling point for water is lower in high-altitude locations.) If it doesn’t, push the reset or calibrate button until it does.

After conducting these two tests, you should have a perfectly calibrated meat thermometer. If your thermometer isn’t accurate and can’t be calibrated, then consider purchasing a new one, especially since they’re so reasonably priced.

How to calibrate an analog thermometer

An analog thermometer can be calibrated using the same methods. It’s easy enough to check the thermometer’s accuracy with the ice water test.

Plunge the tip up to two inches into the center of the iced water and wait several minutes to see how close it measures to 32 ℉ or 0 ℃.
If the reading is off, remove the thermometer from the water and turn it upside down. You’ll see a six-sided nut under the dial — this is the calibration nut — and it can be adjusted using a wrench.
Make a slight adjustment to the nut, and then put the tip into iced water again. It should now be calibrated to 32 ℉ or 0 ℃. If not, then adust the calibration nut again.

You can also calibrate the thermometer to 212 ℉ or 100 ℃ by using the boiling water test. But when you lift the thermometer out of the boiling water and adjust the calibration nut, use protective hand covering. Alternatively, you can wait until the thermometer has cooled, adjust the calibration nut, and retest the thermometer in the boiling water.

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Gene Gerrard, Writer

Gene Gerrard was recently voted as one of the top five personal chefs in Los Angeles. He created About.com's Meat and Wild Game Cooking website and published hundreds of recipes, interviews, cookbook reviews and blog posts about food trends. Gene is also a professional magician, and when he's not writing for Your Best Digs, he's performing at the World Famous Magic Castle in Hollywood.