# Mental Math: From Fahrenheit to Celsius... and Back!

By | Added Dec 8, 2015 (Image: Ilya via Flickr)

Winter break is almost here! If you're spending the holiday season traveling outside the United States, or visiting the United States from somewhere else, you'll probably have to make some adjustments on how you view temperature. This is because the United States remains the only country in the world that measures temperature in degrees Fahrenheit (˚F). Everywhere else in the world, temperature is measured in degrees Celsius (˚C). So, if you live in the United States and travel to another country, you’d have to convert the temperature expressed in ˚C to its equivalent in ˚F to understand how hot or cold it is... unless you get lucky and find a thermometer that uses both units of measure!

Converting temperatures from ˚C to ˚F involves multiplying the temperature in Celsius by 1.8 and adding 32 to your answer. This can take a while to do in your head!
However, we can make a quick estimate by rounding the numbers we use when converting between the two units. Rounding makes it easier to work with the numbers and do the conversion mentally. 1.8 rounded to the nearest whole number is 2, and 32 rounded to the nearest ten is 30. Now here’s what to do:

1.     Take the temperature in degrees Celsius and double it (multiply by 2).

2.     Add 30 to your answer. The sum will be approximately the same temperature in degrees Fahrenheit.

Looking to convert from Fahrenheit to Celsius? Estimate by working backwards using inverse operations! Take the temperature in Fahrenheit, subtract 30, and then divide the answer by 2.

This winter break, where will your travels take you?