Your food thermometer was most likely accurate when you bought it. But measuring instruments generally don’t retain their accuracy forever.
They tend to lose accuracy over time or after damage caused by a drop, extreme temperature or something else.
Every now and then, it’s important to check that your food thermometer is still measuring food temperature accurately. This is essential for your health.
If the temperature probe reads a few degrees higher than the actual meat temperature, you could be exposed to pathogens. If it reads lower, you’ll be overcooking your food. Here are some tips on how to calibrate a food temperature probe.
When Should I Calibrate a Food Thermometer?
- When it’s new, just to make sure it’s accurate from the factory.
- When you’ve not used it for a long time like a few months.
- If you’ve dropped it.
- When the food thermometer has been exposed to extreme cold or heat. It’s also a good idea to calibrate after exposure to rain or high humidity.
- If the food thermometer has been exposed to environmental conditions beyond those specified in the user manual. For instance, if you use a food thermometer not designed for high temperatures in the oven.
- Whenever you have doubts about the accuracy of the thermometer.
How To Check If a Food Thermometer Is Accurate?
Before you calibrate a food temperature probe, you first need to check if it even needs any calibration. To do this, you need to measure something that has a specific known temperature.
There are two such substances you can prepare easily at home: ice water and boiling water.
The Ice Water Method
Add crushed ice to a cup or some other container. Add clean tap water to the ice. A 50:50 ratio of ice and water is ideal.
Leave the mixture for about three minutes. This allows temperature to stabilize.
Dip the food thermometer at least two inches into the ice water. You can put it in deeper than that, as long as the probe doesn’t touch the bottom or sides of the container.
Hold the thermometer in the ice water for 1-2 minutes until it indicates a stable reading. If the temperature is 0°C (32F), your food thermometer is accurate. A deviation of +/- 1 is acceptable, so a reading of -1°C or 1°C is alright (about 30F – 34F).
If the thermometer indicates a temperature below -1°C or above 1°C, it requires calibration. But we recommend repeating the accuracy test with another container of ice water just to be sure.
The Boiling Water Method
Water boils at 100°C (212F) at sea level. Once water boils and reaches that temperature, water turns into steam.
So you can measure boiling water or the steam it releases to determine the accuracy of a food thermometer.
Note that the ice water method is preferable to the boiling water method because of safety. Be extra cautious even when dealing with steam; it can scald you.
Boil water in a container and wait until it has reached a rolling boil. Take a food thermometer and dip it at least 2 inches into the boiling water. Wait 30 seconds to a minute for the thermometer to stabilize.
It should indicate a temperature of 100°C or 212F. However, the reading might be different for people in higher altitudes. Water boils at a lower temperature in a higher altitude because of the reduced pressure.
Use this calculator to determine the exact water boiling point for your altitude. To find your altitude, simply search ‘your town + altitude or elevation’ on Google.
As with the ice water method, allow a deviation of +/-1°C.
How To Calibrate a Food Thermometer?
You can easily calibrate a food thermometer as you check for its accuracy. If you find the thermometer is inaccurate by several degrees, calibrate it immediately using the same ice water or boiling water.
For an analog dial thermometer, there’s a nut underneath the dial that you twist with pliers to adjust the thermometer’s readings.
Adjust the nut only a little at a time and put it back into the water until it indicates a 0°C reading for ice water or 100°C reading for boiling water (or the boiling water temp for your elevation).
For a digital food thermometer, look for the calibration button (usually labelled as CAL). Press this button to enter into calibration mode. You can then offset the thermometer’s reading to bring it back to accuracy.
Check the accuracy of the thermometer again after calibration.
How To Calibrate a Food Thermometer Without Calibration Function?
Not all food thermometers can be calibrated at home. If your food thermometer doesn’t have a calibration function, you have two options.
The easiest is to note by how many degrees the thermometer is off on a piece of tape stuck to the thermometer. Say the thermometer indicates a temperature of 5°C using the ice water method.
Write -5°C on the tape. If it indicates -5°C with the ice water method or 95°C with the boiling water method, write +5°C.
So every time you measure the temperature of meat or some other food, you mentally add or take away the number of degrees indicated on the piece of tape to get the actual temperature.
If it’s a cheap food thermometer though, we recommend buying a new thermometer, preferably one that can be calibrated.
The other option if your food thermometer doesn’t have a calibration function is professional calibration. This is ideal for expensive professional grade food thermometers that you can’t just replace when it gets inaccurate.
Once you’ve ascertained that it is inaccurate, contact the manufacturer and ask if you can send it to them for re-calibration.
If that’s not possible, there are laboratories that offer re-calibration services and will even provide a calibration certificate.
How To Take Care Of a Food Thermometer?
Proper care and maintenance of a food thermometer is essential in its continued accuracy. Here are a few tips for making sure your food thermometer stays accurate and precise for as long as possible.
- Clean the rod or probe after each use as instructed in the user manual.
- Take special care not to damage the rod of the thermometer where the temperature probe is located.
- Check the storage conditions recommended by the manual. Generally, it’s not a good idea to store the thermometer where it’ll be exposed to extreme heat or cold.
- Take care not to drop the food thermometer.
- Only use the food temperature probe as instructed in the manual. If it’s not meant to go into the oven, don’t put it in there. Also, check the min and max temperatures it can measure.