Worry no longer, my friends! There is a much easier way to do it. The only formula you will need is the following:

T1 = (T2+40)*factor - 40.The end.

This formula works for both temperature scales (so {T1,T2} = {F,C} or {C,F}). The only thing you need to remember is whether factor is 5/9 or 9/5. But that is not so hard: there are more degrees between freezing and boiling in Fahrenheit than Celsius, so when you convert to Fahrenheit, you need to use the bigger number, 9/5. Likewise, when converting to Celsius, use 5/9.

Does it really work? Yes! Let's do some examples.

Body temperature is 37 C or 98.6 F. Can we convert to those numbers? Let's start with C to F:

F = (C+40)*9/5 - 40

F = (37+40)*9/5 - 40 = 77*9/5 - 40 = 138.6 - 40 = 98.6Now what about F to C?

C = (F+40)*5/9 - 40

C = (98.6+40)*5/9 - 40 = 138.6*5/9 - 40 = 77 - 40 = 37You can derive the traditional formulas for temperature conversion from this simple one.

F = (C+40)*9/5 - 40 = 9/5*C + 40*9/5 - 40 = 9/5*C + 72 - 40 = 9/5*C + 32

C = (F+40)*5/9 - 40 = 5/9*(F+40 - 9/5*40) = 5/9*(F + 40 - 72) = 5/9*(F - 32)As easy as this formula is, it's still non-trivial to do in your head. So my sister Rachel told me an easy thing to remember about Celsius temperature ranges when it comes to the weather:

- 40+ C: extremely hot (=104+ F)
- 30-39 C: very hot (=86-102 F)
- 20-29 C: comfortable-hot (=68-84 F)
- 10-19 C: cool-comfortable (=50-66 F)
- 0-10 C: chilly (=32-42 F)

So the ideal you'd be most comfortable in is the range around 20-25 Celsius (68-77 F). From there you can see how much the temperature deviates from the ideal. (In Perth, once every couple of years it dips down to freezing, so I did not go any lower on the scale.)

## 1 comment:

The salute of tens is so helpful! Thanks!

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