How to Calibrate a Thermometer

Calibrate a dial stem or digital thermometer using the boiling or ice-point methods.

To ensure that your poultry is cooked to a safe temperature, without drying it out, or to accurately grill a steak to a medium-rare or well-done order, it is important to take a precise temperature reading. This can be accomplished with a properly calibrated food thermometer. Calibrating a thermometer can be done in a matter of minutes with a few supplies found in every kitchen. Calibrate a thermometer after it is purchased, if it is dropped, if it is being used between hot and cold temperature extremes and otherwise, at least monthly.

Things You'll Need

• Thermometer
• Glass
• Crushed ice chips
• Distilled or filtered water
• Cooking pot
• Stove

Instructions

Ice Water Method

1. Fill a glass with as much crushed ice as you can and fill the remainder of the space with distilled or filtered water. If you do not have distilled or filtered water, use clean tap water.

2. Stir the ice chips and water.

3. Insert the thermometer's probe or stem into the middle of the glass so that it is not touching the bottom or sides of the glass. Submerge at least 2 inches of the probe into the ice bath.

4. Hold the stem in the ice bath for 30 to 60 seconds.

5. Adjust the hex adjusting nut under the head or dial of the thermometer so that the temperature reads 32 degrees F, which is the freezing point of water. If you have a digital thermometer, press the reset button to adjust the temperature.

Boiling Water Method

1. Pour tap water into a cooking pot and place it on the heat of a stove top element; bring the water to a rolling boil.

2. Place the stem or probe into the boiling water so that at least 2 inches of the stem is immersed; the stem should not be touching the sides or the bottom of the pot.

3. Hold the stem in the water for 30 to 60 seconds.

4. Adjust the hex adjusting nut under the head or dial of the thermometer so that the temperature reads 212 degrees F, which is the boiling point of water. If you have a digital thermometer, press the reset button to adjust the temperature.

Tips & Warnings

• The University of Nebraska Cooperative Extension recommends using the boiling water method if you usually use the thermometer for hot temperature readings and the ice-water method if you usually use the thermometer for cool temperatures.

• Consider your geographic location; the boiling point of water is 1 degree F lower for every 550 feet rise above sea level, states the South Dakota State University Cooperative Extension Service. For example, at 550 feet above sea level, the boiling point of water is 211 degrees F.

References

• The University of Wisconsin-Madison, Food Safety and Health: Using and Calibrating a Dial Stem Thermometer
• University of Nebraska Lincoln, Extension in Lancaster County: Pass the Taste Test ... Use a Thermometer!
• University of Nebraska Cooperative Extension, Food Safety: Thermometer Calibration
• South Dakota State University Cooperative Extension Service: Calibrating a Food Thermometer