How to Calibrate a Thermometer at Home – Keeping Your Food Healthy and Safe

We all know we should have a thermometer but many of us do not know how to calibrate a thermometer at home. It does not matter if you bought your food from an organic, healthy food conglomerate or if you bought it from the neighborhood grocer, there is always a possibility of a pathogen being on your food. It will not matter how healthy your food is to your body if you can’t come out of the bathroom for three days.

There have been many food safety outbreaks from different pathogens that may have been prevented if foods were cooked to the proper internal temperature or held at the proper temperature. You could be being very diligent in checking your temperatures of meats and things like potato salad, but how do you know if your thermometer is working?

There is a very simple method to check thermometers to be sure they have not come out of calibration. Thermometers can become off-kilter if they are dropped or put into an extremely hot food well out of it’s normal range.

The first thing you will do is get a glass of ice water. Now this next part is very important. You want the mixture to be mostly ice. Many of the food safety books suggest a mixture of 50% water to 50% ice, but I have found that this is not always quite enough. Think of a very wet snowball or a glass of ice water that you can’t really drink because there is too much ice in it.

Let the glass sit for about 3 minutes and then place the stem of your thermometer inside. The temperature of the water at this point is 32 degrees Fahrenheit, or the temperature at which water turns to ice. So, your thermometer should be reading about 1 degree +/- 32 degrees. If it is not and you have a dial stem thermometer, you can adjust it while the stem is in the ice water using the tool that is usually provided, a pair of pliers or just your own fingers. Adjust the dial to read 32 and it is that simple.

If it is a digital thermometer, check the manufacturer’s recommendations for calibration. Some thermometers have to be sent back to the manufacturer for adjustments.

Now that you know how to calibrate a thermometer at home, you can feel more secure that you are keeping your food healthy and your body safe from foodborne illness.