Trick to convert Celsius to Fahrenheit

Living overseas as an American has it’s great points but sometimes it has a lot of challenges that you don’t think about. For instance, most of the rest of the world uses the Metric system. Which makes a lot of sense as the Metric system is much simpler and easier to remember.

That said, if you grew up in America, you likely don’t have the foggiest idea how hot or cold it is when someone gives you a temperature in Celsius. Stay with me here and we’re going to have a quick math lesson so that you can do a basic conversion in your head. Then you won’t look silly having to ask if it is hot or cold the next time someone gives you a forecast.

Double the temperature in Celsius and add 30.
That’s all.

If someone says it was 30 degrees Celsius then you simply double it (to 60) and add another 30 to get 90. 30 degrees Celsius is pretty hot.

If it’s only 10 degrees Celsius then double it (to 20) and add another 30 to get 50. A bit chilly.

If you’re like us and live in the frigid North and someone tells you it’s going to be -30 degrees this weekend, double it (-60) and add 30 to find out it’s…really stinkin’ cold outside.

Incidentally the further you get from freezing the less accurate this is so don’t use this rule for cooking unless you want some unpleasant surprises.

Of course, the reverse is also true. To go from Fahrenheit to Celsius, simply subtract 30 and then divide the remaining value by two. [Corrected thanks to Tim D.]

For those wondering, the real formula is:
Degrees in Fahrenheit = 32 + Degrees in Celsius * ( 9 / 5 )


4 thoughts on “Trick to convert Celsius to Fahrenheit

  1. Handy shorthand ‘trick’ for converting to Fahrenheit!

    But with regards to converting to Celsius:
    “Of course, the reverse is also true. To go from Fahrenheit to Celsius, simply subtract 30 and then double the remaining value.”
    Are you sure? ;:))
    70F – 30 = 40; 2×40 = 80C?

    I think it should be : subtract 30 and divide by 2.
    70F-30 = 40; 40/2= 20C (actual ~21C)

    Keep up the wonderful work! A great website!

    • Hi Tim,

      Thanks for the kind words and the correction. The reverse part was added on late and obviously we didn’t double check it! Have fixed it for future readers. :)