America's Test Kitchen LogoCook's Country LogoCook's Illustrated Logo

How to Test Digital Thermometer Accuracy with Ice Water

You don't need lab-calibrated tools to find out if your kitchen thermometer is accurate. This simple test with ice water does the trick.

Published June 26, 2018.

1. Fill Container with Ice

Start by filling a tall cup or container with ice. ThermoWorks, the maker of our favorite digital thermometer, recommends using crushed ice since it results in less space between pieces of ice than whole cubes would. Make sure to fill the container to the top.

2. Add Water

Slowly add water to the container until all but the top ½ inch of ice is covered with water. Allow it to sit for a couple of minutes. If the ice at the bottom of the container starts to float, you need to add more ice and water.

3. Take the Temperature

Place the thermometer probe into the ice-water mixture. You want to take care to stir it in the center of the container, avoiding the walls of the container. The thermometer should read 32°F in the ice bath, plus or minus the manufacturer’s specified accuracy. If your thermometer can be calibrated, you can adjust it so that it measures 32°F in the ice bath.


Information adapted from 

We’ve recommended a Thermapen for more than a decade, but there’s new competition. Is it still the best digital thermometer?
Get the Review

We made French fries, fried chicken, and caramel sauce, evaluating four thermometers for accuracy, functionality, and durability.
Get the Review


This is a members' feature.