An instant-read thermometer is a key piece of equipment for a well-stocked home kitchen. Accurate temperature readings can mean more than whether a steak is perfectly medium-rare or dry and tough; they can spell the difference between food being safe to eat or not. That’s why having a fast and truly accurate thermometer is essential.
If your instant-read thermometer has been kicking around in your kitchen for months or years, it might be time for a recalibration. It’s actually normal for accuracy to wane, so here’s how to check if your thermometer’s in need of calibration.
What Does Calibration Do?
Calibration is the process of setting a thermometer to the correct temperature. Over time or if it’s dropped or handled roughly, a thermometer’s readings can begin to drift away from accuracy by one or more degrees. By calibrating your thermometer, you’re setting it back to its most accurate state.
How Do You Know When Your Thermometer Needs Calibration?
Knowing when it’s time for a recalibration can be tricky. If your thermometer has drifted by just a degree or two, it can be almost impossible to tell. Our favorite meat thermometer, the Thermapen ONE comes with an accredited calibration certificate, guaranteeing its accuracy upon purchase. Not all brands have such a promise and since drops and jostling (from being shipped to your doorstep for instance) can affect a thermometer’s accuracy, you may want to test it before you start using it in the kitchen.
A good rule of thumb, if you’re worried about the accuracy of your thermometer, is to check it every six months. Some other situations that might warrant more frequent checks are, again, if the thermometer’s severely jostled or dropped or if you use it to check extreme temperature ranges back to back (hot food to cold food or vice versa).
How Do You Calibrate an Instant-Read Thermometer?
While not all instant-read thermometers can be calibrated at home (three of our other recommended models, the Lavatools Javelin Pro Duo, Thermoworks Thermopop 2, and the OXO Good Grips Thermocouple Thermometer can be reset to factory settings, not recalibrated), the Thermapen ONE can be adjusted relatively simply. First, you’ll need to remove the label on the back to gain access to the two calibration adjustment screws. The screw closest to the hinge is the “zero” adjustment screw. The one closer to the battery compartment is the “span” screw. For more details, see the calibration manual from Thermoworks here. Have a small, slotted screwdriver on hand to perform any necessary adjustments.
There are two common tests that you can perform at home to test the accuracy of your thermometer. The first is an ice bath to see if your thermometer will accurately measure the target temperature of 32°F. Fill an insulated container with “crushed or pebble ice, the smallest ice you can find will give you the best results.” says Kyle Halvorson, Consumer Marketing Manager at Thermoworks. Then add just enough water to cover the ice. “The biggest factor is to make sure the ice is not floating,” Halvorson says. “Fill that cup up with ice, add some water and if your ice comes off the bottom of the glass, dump some water out. You’re only getting that 32 degrees [Fahrenheit] in the transition between ice and water. If you’ve got a bunch of water at the bottom and no ice that’s actually going to be warmer…you don’t want your probe to rest on ice and you don’t want it to be in a pocket of water.” Once you’ve got a proper ice bath, gently stir with the probe, which will help create a uniform atmosphere and give you the most accurate reading. Once the display has stabilized you can adjust the temperature reading on the thermometer by rotating the “zero” screw until the display reads 32°F.
If you want to double-check your thermometer’s accuracy, you can also test your thermometer in boiling water. This test requires some extra research to do correctly. The temperature at which water boils differs depending on a few factors. In order to precisely calibrate your thermometer you’ll need to know your altitude and the barometric pressure of your location, as they both affect the boiling point of water. “We do have a boiling point calculator on our website where you can put in your elevation and your barometric pressure, which changes from day to day (you can look it up online), and [the Thermoworks boiling point calculator] will tell you to the decimal to a tenth of a degree what your boiling point is so that you can accurately check [your thermometer’s accuracy],” says Halvorson.
How Often Should You Calibrate an Instant-Read Thermometer?
While in a restaurant kitchen, it may be necessary to calibrate thermometers as often as every day, at home thermometers are seeing much less wear and tear. That said, how often you calibrate your thermometer depends on what kind of thermometer you have and how you care for it. In the case of our winner, ThermoWorks doesn’t recommend any specific timeline. “That really depends on what environment are you using it in. Is it a harsh environment in a toolbox getting thrown around or is it in a lab where it’s getting put on a shelf with styrofoam padding? Really it’s going to be up to the end user. If they want to do it every week they’re more than welcome to do that but my philosophy is to trust the Thermapen,” Halvorson says.
Can every thermometer be calibrated?
Unfortunately, no. While many instant-read thermometers have either a screw to allow manual recalibration or a reset button to return it to factory settings, some models cannot be recalibrated at all. In these instances, we recommend contacting the manufacturer for guidance. In some cases, you can send your thermometer back for recalibration or replacement.
What’s the best instant-read thermometer?
Our favorite instant-read thermometer is the ThermoWorks Thermapen ONE for its quick readings and its large screen with a rotating illuminated display. If you’re on a budget we recommend the ThermoWorks ThermoPop 2 and Lavatools Javelin Pro Duo Digital Instant-Read Thermometer. For more, check out our full review here.
Why We’re the Experts
- Andrea Rivera Wawrzyn is a freelance food writer and recipe developer and was formerly an associate editor at America’s Test Kitchen.
- She has developed recipes for multiple New York Times bestselling cookbooks, including an IACP award winner.
- We’ve independently tested instant-read thermometers, meat thermometers, wireless grill thermometers, and more.
- For this article, we reached out to Kyle Halvorson, the Consumer Marketing Manager at Thermoworks, for tips on calibration.
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