How Do I Calibrate My Thermometer?

Maple syrup is said to be finished when it reaches 7ºF above the boiling point of water. A 0 – 50 Maple Thermometer is used with a maple evaporator to monitor progress. Since the boiling point of water fluctuates with barometric pressure and other environmental factors, many folks make it a practice to calibrate their Maple Thermometer before starting up their evaporator each day.

Abbreviated instructions for calibration are noted on the face of your Maple Thermometer. For more detailed and illustrated instruction, please download our INSTRUCTION SHEET.

In a nutshell, you place the stem of your thermometer in boiling water so that the stem is immersed up to the dimple mark. You will let the arrow on the dial make a full revolution and then use the screw on the back of the dial to make adjustments to the calibration. The arrow should be pointing to “0” in boiling water.


  1. Maple thermometers are great for monitoring progress while boiling, but you should always rely on a hydrometer and Murphy Cup for best precision/accuracy.
  2. To achieve the best readings, the thermometer needs to be clean. The stem should be clear of mineral deposit build-up.
  3. The stem of the thermometer should be immersed up to the dimple mark.
  4. Barometric pressure can shift throughout the day. By taking periodic hydrometer tests, you can make adjustments to when you draw off. For example, if you know that the Thermometer is regularly pointing to the “8” when you have reached perfect density, then draw off at the “8” instead of the “7”. Using your hydrometer and Murphy Cup, you can adapt accordingly throughout the day.