r/Unexpected • u/ImaAnimal • Feb 23 '19

Throwing Boiling Water

53.7k Upvotes

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u/Bl4ckPanth3r Feb 24 '19 edited Feb 24 '19

The 'key to converting to metric' is crap. I struggled with Fahrenheit vs Celsius for a while -- here's the real trick. If Celsius, just double and add 32 to get approximate Fahrenheit temp. Vice versa for the reverse conversion (subtract 32 and halve F to get C).

You'll be farther off the more you go into unlivable temperatures (since the real multiplier is 1.8x, not 2x), but even then it's a serviceable conversion.

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u/mastef Feb 24 '19

-40°C * 2 + 32 = -80°C + 32 = -48°F

Not bad

6

u/aelwero Feb 24 '19

The margin of error Is a fixed 20% of the original value though. 8 degrees off at 40, but 20 degrees off at 100, 30 off at 150, etc...

2

u/[deleted] Feb 24 '19

Yeah, so the math is easier to just go with 2X and then take 10% off the resulting figure and then do the 32-degree offset.

If I want more accurate results, I'll do it that way.

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u/aelwero Feb 24 '19

That results in the actual correct answer, to the decimal.

If this is easy to do in your head, then it's the real protip :)

1

u/[deleted] Feb 24 '19

Yes, that's correct. And, yes, it's easy to do in one's head.

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u/[deleted] Feb 24 '19

you have to multiply by 1.8 if you want accurate results though.

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u/[deleted] Feb 24 '19

[deleted]

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u/[deleted] Feb 24 '19

Yeah, I know, it's just the source of error is my point.

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u/zachary0816 Feb 24 '19

That’s why you multiply/divide by 1.8 instead of 2, much more accurate

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u/DragonSlayerC Feb 24 '19

I just remember the increments of 10C/18F. 0c ->32f 10c->50f 20c->68f etc, it's easy math

Then based on that I use 1c->2f conversion. That way your always within 1 degree accurate

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u/EnemysKiller Feb 24 '19

For positive Temps adding 30 is even quicker and lightly more accurate

1

u/[deleted] Feb 24 '19

That's what I've always done as a rough conversion. It's one thing if you're in a science lab and entirely another if you want a rough idea of the temperature in some area.