Converting fahrenheit to celsius

[thescreensavers]

F to C


100C --- Xc
____ = ___
212 F --- 78F


(--- used as spacing)

Work properly?

If I do it on my phone is gives me 25.56C- the correct answer according to google is 25.56, but why does the formula not work out correctly?


If I use my calculator with that formula I get 36.79??


Why, thanks

 

[Anubis]

im gonna guess its a order of operations issue, either your phone or calc is doing something out of order

 

[Brainonska511]

Why not use this one?

[°F] = [°C] · 9/5 + 32 or [°C] = ([°F] - 32) · 5/9

 

[Born2bwire]

Because it's wrong.

F = 1.8*Grad+32

There's a DC offset of 32 degrees Fahrenheit at freezing. You can't assume that they are related purely by a ratio.

 

[skrilla]

Probably because that is not the correct formula to convert Fahrenheit to Celsius.

 

[thescreensavers]

Originally posted by: Brainonska511
Why not use this one?

[°F] = [°C] · 9/5 + 32 or [°C] = ([°F] - 32) · 5/9

I know this is the proper way but why does my formula not work?

 

[Triumph]

What is this mess? Why not just use:

F = 1.8C + 32.

There, easy to estimate in your head. Double the Celcius, add 32, and you're within a few degrees.

 

[Brainonska511]

nm

 

[Modelworks]

Never used that formula.
Much simpler to subtract 32 from F
Then multiply times .556

Works as long as you dont need lots of precision.

So 80F - 32 = 48
48 x .556 = 26.6 C

 

[Triumph]

Originally posted by: thescreensavers

Originally posted by: Brainonska511
Why not use this one?

[°F] = [°C] · 9/5 + 32 or [°C] = ([°F] - 32) · 5/9

I know this is the proper way but why does my formula not work?

Because the deviations between 1 deg C is not the same as the deviation between 1 deg F.

 

[FoBoT]

you can't make up your own science

 

[Born2bwire]

Originally posted by: FoBoT
you can't make up your own science

Bullshit, I've been published!

 

[Anubis]

personally i just do the C*2+30 method and its close enough, unless its important then i just google it and let it do the math for me

 

[hypn0tik]

Originally posted by: thescreensavers

Originally posted by: Brainonska511
Why not use this one?

[°F] = [°C] · 9/5 + 32 or [°C] = ([°F] - 32) · 5/9

I know this is the proper way but why does my formula not work?

Because there is an offset between C and F. 0 C = 32 F, so when you convert, you need to take into account that offset.

You can graph it (C on one axis, F on the other) and you'll see that it doesn't pass through the origin.

 

[bonkers325]

the relationship between F and C is not linear, therefore the formula u are using is incorrect

 

[Pugnax]

Yep that's correct. While they both measure temperature, their unit size is different, hence the required conversion.
Your ratio doesn't work because...basically you aren't converting the temperature...just picking one set of equal points on the scales and trying to linearly extrapolate another temperature, that ratio is not such.

 

[sandorski]

Stop using Fahrenheit, problem solved.

 

[oboeguy]

Originally posted by: bonkers325
the relationship between F and C is not linear, therefore the formula u are using is incorrect

Fail! It is linear but the OP is missing a constant term.

 

[potoba]

Originally posted by: thescreensavers
F to C


100C --- Xc
____ = ___
212 F --- 78F


(--- used as spacing)

Work properly?

If I do it on my phone is gives me 25.56C- the correct answer according to google is 25.56, but why does the formula not work out correctly?


If I use my calculator with that formula I get 36.79??


Why, thanks

because they're offset by a constant!!!

 

[nycxandy]

Originally posted by: oboeguy

Originally posted by: bonkers325
the relationship between F and C is not linear, therefore the formula u are using is incorrect

Fail! It is linear but the OP is missing a constant term.

Correct!

 

[imported_Lothar]

Originally posted by: sandorski
Stop using Fahrenheit, problem solved.

Better yet, use Kelvin.