KISS: F to C, Simple as Can Be

The United States still uses Fahrenheit to measure the weather. Rest of the world? Celsius (it is better!).

The US is not the same. That is pretty lame.

But we can deal, see? And get to where things need to be: converting Fahrenheit to Celsius and Celsius to Fahrenheit with the simplest of math for you and me.

(Yes, I know proper grammar – we are running with the rhymes not matter!)

  1. F to C
  2. C to F
  3. Feel Better Celsius
  4. What’s Left?

F to C

( F – 30 ) / 2 = C

e.g. ( 70F – 30 ) / 2 = 20C

Degrees in Fahrenheit, minus thirty, divided by two; that’s Celsius for you!

C to F

C * 2 + 30 = F

e.g. 20C * 2 + 30 = 70F

Double the degrees, add thirty right, you’ll get Fahrenheit!

Feel Better Celsius

Forget that simple math, for real? No worries! Use this that gives you Celsius’s feel:

30 is HOT 🔥

20 is Nice ~

10 is Cold 🥶

0 is Ice 😱

Celsius Limerick

What’s Left?

If you will be scientific, the equation needs to be specific:

F = C * 9 / 5 + 32

C = ( F – 32 ) * 5 / 9

Textbook F and C Conversions

5 by 9 is .56 and 9 by 5 is 1.8 – for mental calculations, these equations aren’t great 😑

So 5 by 9 is near to half, 1.8 two, using 30 by rounding gives good enough approximations for me and for you! We can show it’s true:

  • 100C ~ 230F (expected: 212F)
  • 30C ~ 90F (i.e. 86F)
  • 20C ~ 70F (68F)
  • 10C ~ 50F (50F)
  • 0C ~ 30F (32F)
  • -10C ~ 10F (14F)

That is it! That is all you need. Take these equations with you to do conversions at speed.

Until all the world uses Celsius we will live with the muss. At least this basic algebra removes a bit of the fuss.

Thank you for sitting through my rhymes – here is to you! Cheers to our next time.

Published by

Jimmy Chattin

Processor of data, applier of patterns, maker of games and stories.

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