How to Change a Digital Thermometer to Different Units

A thermometer in the foreground with a blurry child in the background.
  • 1 hours
  • Beginner
  • 25
What You'll Need
Digital thermometer
Temperature conversion sheet
Conversion app for the phone
What You'll Need
Digital thermometer
Temperature conversion sheet
Conversion app for the phone

The average home medical kit is not complete without a properly functioning digital thermometer. These useful devices can accurately read a person’s body temperature within a one-degree margin of error. However, sometimes digital thermometers come preset with an unfamiliar unit of temperature. Fortunately, changing a digital thermometer to a different unit system is easy and can be accomplished by following these simple steps.

Step 1 - Consult the Owner’s Manual

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The owner’s manual will inform you if the device is capable of changing units of measurement. If you no longer have access to the manual and cannot find it online, then you will need to play around with the thermometer to see if changing the units of measurement is even possible. Scrolling through the menu options or holding down the power button should let you know if changing units is an option.

Step 2 - Power on the Thermometer

Most digital thermometers only come equipped with one button. In order to change the units on the device, you will need to make sure the thermometer is powered on. If the device is working properly, then you should be able to change the units of measurements with little hassle. If the thermometer fails to power on, then double-check the battery and ensure that it is installed properly and has not expired.

Step 3 - Change the Units

You will need to consult the owner’s manual to determine the fastest way to change the measurement units on your digital thermometer. This typically involves holding down the power button or navigating to a menu, though some devices, like cooking thermometers, feature a button that switches between Celsius and Fahrenheit. Proceed to the following steps if your thermometer does not have the ability to change units.

Step 4 - Manually Changing Units

If you cannot figure out how to change the measurements on your digital thermometer, or if the device cannot convert the units automatically, then you will have to convert the temperature the old fashioned way. Fortunately, making the conversion manually is a simple process that only requires a calculator and a few math skills.

Step 5 - Converting from Celsius to Fahrenheit

The mathematical equations for converting Celsius temperatures to Fahrenheit is fairly straightforward. There are two different ways to convert to Fahrenheit. First, you can multiply the Celsius temperature by 1.8 and then add 32. Second, you can multiply the original by 9, then divide the result by 5 and add 32. Both equations will result in a successful conversion. Pick the method that is easiest to remember for quicker access.

Step 6 - Converting from Fahrenheit to Celsius

Changing the temperature from Fahrenheit to Celsius is a little more involved. There are three equations you can use for the conversion. In all three equations, the first step is to subtract the Fahrenheit temperature by 32. Then, you can either multiply the result by 5 and divide by 9, or divide the result by 9 and multiply by 5. You can also take the result and divide by 1.8. The hardest part about these conversions is remembering which numbers to use and the correct order of operation.

Step 7 - Use a Conversion Chart

If you do not want to memorize the equations, then consider printing a conversion chart for quick reference. You can find these Fahrenheit to Celsius conversion charts—and vice versa—online. Simply print out a copy and tape it on the inside door of your medicine cabinet. Remember, there are plenty of charts available online, but choose one that focuses on the temperature range of your digital thermometer, which typically is from 90° F to 111.9° F.


In addition to printing out a conversion chart, online converters are another useful option for changing units of measurements manually. You can find these converters via a search engine and most are free to use. Furthermore, there are free apps available for your phone that will convert these units on the fly. Whenever using these services, it's a good idea to double-check their accuracy by using known measurements, like the boiling point of water, which is 212° Fahrenheit and 100º Celsius.

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