thermometer

How to convert Fahrenheit to Celsius?

Converting Fahrenheit to Celsius doesn’t require a calculator. Here are some easy-to-remember temperatures if you’re accustomed to Fahrenheit temperatures…

  • 10F is approximately -10C
  • 32F = 0C (melting point of water)
  • 40F is approximately 4C
  • 70F is approximately 20C
  • 100F is approximately 40C

Converting Fahrenheit to Celsius

  1. Take your Fahrenheit temperature, and subtract 32 from it. Let’s say the temperature is 50F. Our result is then 50 – 32 = 18.
  2. Multiply the result by 5. In our example, we do the multiplication and get 18 x 5 = 90.
  3. Divide the result by 9 to get our final Celsius result, 90/9 = 10C.

Fahrenheit to Celsius formula: (F-32) * 5 / 9 = C

Convert Celsius to Fahrenheit

  1. Take your Celsius temperature, and multiply by 9. Let’s say the temperature is 25C. Our result is then 25 * 9 = 225.
  2. Divide the result by 5. In our example, we do the division and get 225 / 5 = 45.
  3. Add 32 to the result to get our final Fahrenheit result, 45 + 32 = 77.

Celsius to Fahrenheit formula: C * 9/5 + 32 = F

Why is -40F = -40C?

Oddly enough, -40F is not colder than -40C. Yes, they are both really cold, but they are also exactly the same temperature. Let’s use the formulas from above and try it out.

Convert -40F to Celsius

  1. (F-32) * 5 / 9
  2. (-40-32) * 5 / 9
  3. -72 * 5 / 9 = -40

Convert -40C to Fahrenheit

  1. (C * 9 / 5) + 32
  2. (-40 * 9 / 5) + 32
  3. -72 + 32 = -40

Exactly the same!

Comments 4

    1. Ray Li

      Thanks for those links, Andrew. Also, the rough approximation of doubling and then adding 30 is fantastic. I’ll be updating the post soon with those details.

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