Kelvin to Celsius Converter (K to °C)
Convert kelvin to celsius instantly, with the formula, a reference table and the temperatures that actually matter.
The formula
Temperature scales do not share a zero point, so this is not a simple multiplication:
°C = K − 273.15Kelvin to Celsius table
| Kelvin | Celsius |
|---|---|
| -40K | -313.15°C |
| -20K | -293.15°C |
| -10K | -283.15°C |
| 0K | -273.15°C |
| 10K | -263.15°C |
| 20K | -253.15°C |
| 25K | -248.15°C |
| 30K | -243.15°C |
| 37K | -236.15°C |
| 40K | -233.15°C |
| 50K | -223.15°C |
| 60K | -213.15°C |
| 70K | -203.15°C |
| 80K | -193.15°C |
| 90K | -183.15°C |
| 100K | -173.15°C |
Temperatures worth knowing
- Water freezes at 0°C
- Water boils at 100°C
- Normal body temperature is about 37°C
- A comfortable room is around 21°C
Where each scale is used
Fahrenheit survives in everyday use in the United States and in a handful of smaller territories. Everywhere else reports weather, cooking and body temperature in Celsius — including the United States itself once you move into science, medicine or engineering. Kelvin is the scientific standard because it starts at absolute zero, the point where there is no thermal energy left to remove, which makes it the only one of the three where ratios mean anything: 200 K really is twice as warm as 100 K, while 20°C is not twice 10°C.
Oven temperatures are their own small trap. British recipes often give gas marks instead of degrees, and fan or convection ovens run about 20°C hotter than the number suggests, so a recipe written for a conventional oven needs lowering rather than converting.
Doing it in your head
For Celsius to Fahrenheit, double it and add 30. For 20°C that gives 70 against a true 68 — close enough to decide what to wear. Going the other way, subtract 30 and halve. The shortcut drifts at the extremes because it ignores the difference between doubling and multiplying by 1.8, so use the calculator for anything that matters: an oven, a fever, or a technical specification.
Common questions
Why is there a −32 in the formula?
Because the two scales disagree about where zero is. Fahrenheit puts the freezing point of water at 32 rather than 0, so that offset has to be removed before the ratio between degree sizes is applied. A degree Celsius is also larger than a degree Fahrenheit — nine Fahrenheit degrees span the same range as five Celsius degrees — which is where the 9/5 comes from.
At what temperature do the scales meet?
Celsius and Fahrenheit read the same at −40. It is the one temperature where you do not need to convert at all, and a useful sanity check: if your conversion does not agree at −40, you have applied the offset in the wrong order.
Can a temperature be negative in Kelvin?
No. Kelvin starts at absolute zero, so there is nothing below it. If a conversion produces a negative Kelvin value, the input was below −273.15°C, which is not a physically possible temperature.