How to Calibrate Your Thermometer

If you’re anything like me, you’ve probably got a handful of thermometers dancing around your drawer of miscellaneous kitchen tools.  But, are they accurate?  If you’re roasting a turkey, a degree or two of inaccuracy isn’t going to make a dramatic difference.  But, if you’re making caramel, tempering chocolate, cooking sous vide, grilling a steak, or doing any number of other tasks that require a precise temperature, having a thermometer you can trust is clutch. 

Calibrating your thermometer is quick and easy.  Many analog and digital thermometers allow you to offset the temperature to adjust for the calibrated value.  However, if your thermometer doesn’t offer an offset function, a piece of blue tape with the delta will work just fine. 

Method 1: Ice Water

1. Fill a glass with ice cubes, then top off with cold water. 
2. Stir the water and let sit for 3 minutes.
3. Stir again, then insert your thermometer into the glass, making sure not to touch the sides. 
4. The temperature should read 32°F (0°C).  Record the difference and offset your thermometer as appropriate.

Method 2: Boiling Water

1. Boil a pot of distilled water.
2. Once the water has reached a rolling boil, insert your thermometer, making sure not to touch the sides or bottom of the pot.
3. The temperature should read 212°F (100°C).  Record the difference and offset your thermometer as appropriate.
   [Note: The boiling point of water will vary with altitude.  Use this handy water boiling point calculator to find the right temperature for your elevation.]

Now that you’ve got a thermometer you can trust, go forth and cook with confidence!