this post was submitted on 02 Nov 2025
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LPT: Easy way to convert Celsius to Fahrenheit (lemmy.world)
submitted 2 days ago by xylogx@lemmy.world to c/lifeprotips@lemmy.world
12 comments fedilink hide all child comments
 

Double the number, then reduce by one-tenth the doubled number, then add 32

Example: To convert 25 C double it to 50, reduce by 5 to get 45, then add 32 to get 77 F.

The reason this works is because 9/5 = 10/5 - 1/5. And the nice thing about this is that it is an exact conversion not an estimation.

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[–] ook@discuss.tchncs.de 31 points 2 days ago (1 children)

"Easy"

[–] xylogx@lemmy.world 10 points 2 days ago (1 children)

Ok maybe a bit of a stretch, but definitely easier than directly calculating 9/5ths.

[–] panda_abyss@lemmy.ca 10 points 2 days ago (1 children)

9/5 is easy though, you double then subtract a tenth

[–] MoreZombies@quokk.au 18 points 2 days ago

Why would I want to convert TO Fahrenheit? =/

[–] hypeerror@sh.itjust.works 11 points 2 days ago

every 10 degrees Celcius is 18 Fahrenheit.

0c is 32

10 c is 32 + 18 or 50f

20c is 50 + 18 or 68f

30c is 68 + 18 or 86f

40c is 86 + 18 or 104f

Congrats you can now dress comfortably when you travel.

[–] iAmTheTot@sh.itjust.works 7 points 2 days ago* (last edited 2 days ago)

It's even easier to skip the "reduce by 1/10" step and you still get close. It gets less and less accurate the larger the number becomes, but most people are doing this for day-to-day outdoor temps and it's more than good enough for that to get close. Maybe don't rely on it for baking, though.

edited to add, also instead of "adding 32" it's often easier to think about just adding 30.

[–] BeigeAgenda@lemmy.ca 4 points 2 days ago

Is searching for "25 C in F" considered cheating?

[–] BlueberryWalnut@sopuli.xyz 3 points 2 days ago

Just double it

[–] sin_free_for_00_days@sopuli.xyz 2 points 2 days ago

I rarely care about the actual number. "Cold", "Not bad", "Warm", and "Hot" cover 99% of my weather related temperature interactions. I have also memorized 3 easy conversion points to estimate from if I care. If I really care...well I don't think that I ever have. Maybe cooking instructions, then I might care, but even that is usually just by feel. I'm not a baker.

10C = 50F 
28C = 82F
40C = 104F
[–] InvestBurnout@fedia.io 2 points 2 days ago (1 children)

I always multiply by 2 and add 30

[–] SanctimoniousApe@lemmings.world 2 points 2 days ago

Good enough for estimating, but not accuracy.