At what temperature should a thermometer be calibrated?

The correct temperature for calibrating a thermometer is 0 degrees Celsius, which is the freezing point of pure water. Calibration at this particular point is critical for ensuring the thermometer provides accurate readings in the temperature range commonly encountered in food safety practices. When a thermometer reads 0 degrees Celsius accurately, it indicates that it is properly set to measure other temperatures reliably, including those necessary for safe food handling and storage.

Calibrating at freezing point allows for a simple and practical method because water freezes at this temperature under standard atmospheric conditions. Accuracy at this point can also often be checked by submerging the thermometer in ice water, which is a straightforward, accessible solution in many environments.

Other temperatures mentioned, such as -18 degrees Celsius (which is below the freezing point), 25 degrees Celsius (room temperature), and 100 degrees Celsius (boiling point of water), do not serve as practical calibration points for the majority of food safety applications. Each has its specific use in different contexts but is less ideal for the general calibration of thermometers intended for food safety.