37 Degrees Celsius to Fahrenheit, Kelvin and Rankine

Four scales, one reading, in a nutshell

Type a temperature, say which scale it is written in, and all four come back at once: Celsius, Fahrenheit, Kelvin and Rankine. A recipe calling for 180 °C is 356 °F, a weather app showing 68 °F is 20 °C, and a lab sheet quoting 300 K is 80.33 °F. Negative values are fine, and the only floor is absolute zero.

-40

the one reading where Celsius and Fahrenheit agree

180

Fahrenheit degrees between freezing and boiling, against 100 Celsius

273.15

Kelvin at the freezing point, the offset that makes the scale absolute

459.67

Rankine degrees below zero Fahrenheit before motion stops

Two fields, and what the result adds

1
Type the number. Decimals and minus signs both work, so -17.78 and 98.6 are equally valid.
2
Pick the scale it came from. The tile for that scale is highlighted in the answer so you can see at a glance which one was the input.
3
Read across. Under the four tiles sit the formulas with your own number in them, a plain-language note on what that temperature is, and a table of fixed points with the nearest one marked.

Why the arithmetic looks lopsided

Every conversion here is a stretch plus a shift. Celsius and Fahrenheit disagree on both: they start in different places and their degrees are different sizes, since 180 Fahrenheit degrees cover the same span as 100 Celsius degrees. That ratio, 9/5, is the stretch, and the 32 is the shift. Kelvin skips the shift against Celsius and just moves the zero down to where molecular motion stops, which is why the degree sign is dropped: a Kelvin is not a degree of anything, it is a unit on an absolute scale. Rankine does the same trick to Fahrenheit, so it is the scale US thermodynamics texts reach for when an absolute temperature is needed without leaving customary units.

The conversions, with a worked example each

From, to	Formula	Worked example
C to F	F = C x 9/5 + 32	180 x 1.8 + 32 = 356
F to C	C = (F - 32) x 5/9	(98.6 - 32) x 0.5556 = 37
C to K	K = C + 273.15	25 + 273.15 = 298.15
F to R	R = F + 459.67	70 + 459.67 = 529.67
K to R	R = K x 9/5	300 x 1.8 = 540

Temperatures worth knowing by heart

What it is	°F	°C	K
Home freezer	0	-17.78	255.37
Water freezes	32	0	273.15
Refrigerator shelf	39.2	4	277.15
Room temperature	70	21.11	294.26
Body temperature	98.6	37	310.15
Water boils	212	100	373.15
Oven, roasting	350	176.67	449.82

Three facts that explain the odd numbers

Zero Fahrenheit was a freezing brine, not a freezing river. The scale was anchored on a salt and ice mixture, which is as cold as you could reliably get in a workshop at the time, and that is why 0 °F is -17.78 °C rather than a round figure.

-40 is the crossing point. Because one scale gains 1.8 degrees for every degree of the other and starts 32 higher, the two lines meet exactly once, at -40. It is the only temperature you never need this page for.

A degree of difference is not the same as a temperature. Warming something by 1 K and by 1 °C are identical, and by 1 °R is identical to 1 °F, even though the readings themselves are hundreds apart. That is why heat capacity tables quote J per kg per K and nobody converts the K.

The questions the scales keep raising

Is there a quick way to do this in my head?

Double the Celsius and add 30. It puts 20 °C at 70 against a true 68 °F, which is close enough for deciding on a jacket and useless for an oven. The error grows with the temperature, reaching 38 degrees by the time you are at 200 °C, where the shortcut says 430 against a true 392.

Why does Kelvin have no degree sign?

Because it measures from an absolute floor rather than from an arbitrary anchor, so a value is a quantity of thermal energy rather than a position on someone's scale. Writing 300 K is correct and "300 degrees Kelvin" is not. Rankine keeps the degree sign by convention even though it is also absolute.

Can a temperature be below absolute zero?

Not on this scale. 0 K is -273.15 °C and -459.67 °F, and the converter refuses anything under it rather than printing a negative Kelvin. Laboratories have reached within a billionth of a degree of it and never past it.

Which oven setting matches a European recipe?

The usual four: 160 °C is 320 °F, 180 °C is 356 °F and most US ovens round that to 350, 200 °C is 392 °F which rounds to 400, and 220 °C is 428 °F. Fan settings usually run about 20 °C lower than the same recipe without one.

Does water always boil at 212 °F?

Only at sea level. Boiling point falls by roughly 1 °F for every 500 ft of elevation, so in Denver water boils near 202 °F and pasta takes longer. Pressure, not heat, is what changes.

Where would I ever meet Rankine?

In US thermodynamics: gas turbine cycles, refrigeration work and steam tables written in customary units. Any formula needing an absolute temperature breaks with Fahrenheit in it, and Rankine fixes that without switching the whole calculation to metric.

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What is 37 degrees Celsius in Fahrenheit?

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