Temperature Converter

By Inch To Cm Converter Editorial Team·August 31, 2026·2 min read

Temperature is the odd one out among conversions: because Celsius and Fahrenheit start counting from different zero points, you cannot just multiply by a factor. To go C to F you multiply by 9/5 and then add 32; F to C you subtract 32 first, then multiply by 5/9. Kelvin simply shifts Celsius down by 273.15.

The formulas, and a shortcut

From → To	Formula
C → F	F = C × 9/5 + 32
F → C	C = (F − 32) × 5/9
C → K	K = C + 273.15
K → C	C = K − 273.15

For a rough C-to-F in your head: double the Celsius and add 30. It is a few degrees off in the middle of the range (20°C → 70 vs the true 68°F) but fine for weather.

Reference points worth knowing

Reference	°C	°F	K
Absolute zero	−273.15	−459.67	0
Water freezes	0	32	273.15
A cool room	20	68	293.15
Body temperature	37	98.6	310.15
Water boils (sea level)	100	212	373.15

−40 is the one temperature where Celsius and Fahrenheit read the same.

Kelvin, Rankine and when they matter

Kelvin is the science unit – written without a degree symbol (300 K, not 300°K) because it is an absolute scale. Rankine is Kelvin’s Fahrenheit-flavoured cousin, still seen in some US engineering. For everyday use you will only ever need C and F. If you also need to convert an oven size or a length on the same recipe or plan, the cooking converter and length converter are alongside.

FAQ

How do I convert Celsius to Fahrenheit?

Multiply the Celsius value by 9/5 (1.8) and add 32. Example: 20°C → 20 × 1.8 + 32 = 68°F.

How do I convert Fahrenheit to Celsius?

Subtract 32, then multiply by 5/9. Example: 98.6°F → (98.6 − 32) × 5/9 = 37°C.

At what temperature do Celsius and Fahrenheit meet?

At −40. −40°C equals −40°F exactly.

Why is Kelvin written without a degree symbol?

Kelvin is an absolute scale, not a relative one, so by convention it takes no degree sign - 273 K, not 273°K.

What is absolute zero?

The lowest possible temperature, where thermal motion stops: 0 K, −273.15°C, or −459.67°F.