Temperature Converter
Celsius, Fahrenheit and Kelvin, live both ways โ with the landmarks chart.
About this converter
Type in any of the three boxes โ Celsius, Fahrenheit, Kelvin โ and the others follow instantly, with a plain-language readout of what that temperature feels like. Below it, the landmark chart worth actually memorising, from โ40ยฐ (the one temperature where both scales agree) to a moderate oven.
The formula, and the trick
Exact: ยฐF = ยฐC ร 9/5 + 32 โ Fahrenheit degrees are five-ninths the size of Celsius degrees and the scale starts 32 lower, which is why the conversion needs both a multiply and a shift. In your head: double it and add 30 lands within a couple of degrees anywhere between freezing and body heat (20 ยฐC โ 70 vs the true 68). Kelvin is Celsius with the zero moved to absolute zero, โ273.15 ยฐC โ same degree size, no negative numbers, which is why science uses it. The three worth knowing cold: 0 ยฐC = 32 ยฐF (freezing), 37 ยฐC = 98.6 ยฐF (body), 100 ยฐC = 212 ยฐF (boiling).
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32: 20 ยฐC ร 1.8 + 32 = 68 ยฐF. The quick mental version โ double and add 30 โ gets within a couple of degrees for everyday weather.
What temperature is the same in both scales?
โ40ยฐ. It's the crossover point where ยฐC and ยฐF read identically โ and a favourite exam question for exactly that reason.
What is normal body temperature in both scales?
37 ยฐC = 98.6 ยฐF, with normal variation of half a degree Celsius either way through the day. Fever conventionally starts at 38 ยฐC / 100.4 ยฐF.
Why does science use Kelvin?
Kelvin starts at absolute zero (โ273.15 ยฐC), so temperatures can't go negative and ratios mean something physically โ 200 K really is twice as hot as 100 K in energy terms, which isn't true of 20 ยฐC versus 10 ยฐC.