Units
Temperature converter
Celsius to Fahrenheit, kelvin and the rest. With the offset applied properly, which is where many tools go wrong.
Conversions are worked out on your own machine. No sign-up, no waiting and nothing sent anywhere.
Common conversions
| degree Celsius | degree Fahrenheit |
|---|---|
| -40 °C | -40 °F |
| -10 °C | 14 °F |
| 0 °C | 32 °F |
| 10 °C | 50 °F |
| 20 °C | 68 °F |
| 25 °C | 77 °F |
| 30 °C | 86 °F |
| 37 °C | 98.6 °F |
| 100 °C | 212 °F |
| degree Fahrenheit | degree Celsius |
|---|---|
| -40 °F | -40 °C |
| -10 °F | -23.333 °C |
| 0 °F | -17.778 °C |
| 10 °F | -12.222 °C |
| 20 °F | -6.6667 °C |
| 25 °F | -3.8889 °C |
| 30 °F | -1.1111 °C |
| 37 °F | 2.7778 °C |
| 100 °F | 37.778 °C |
| degree Celsius | kelvin |
|---|---|
| -40 °C | 233.15 K |
| -10 °C | 263.15 K |
| 0 °C | 273.15 K |
| 10 °C | 283.15 K |
| 20 °C | 293.15 K |
| 25 °C | 298.15 K |
| 30 °C | 303.15 K |
| 37 °C | 310.15 K |
| 100 °C | 373.15 K |
| kelvin | degree Celsius |
|---|---|
| -40 K | -313.15 °C |
| -10 K | -283.15 °C |
| 0 K | -273.15 °C |
| 10 K | -263.15 °C |
| 20 K | -253.15 °C |
| 25 K | -248.15 °C |
| 30 K | -243.15 °C |
| 37 K | -236.15 °C |
| 100 K | -173.15 °C |
Worked out with the same factors the converter above uses.
Temperature is the only category on this site that does not convert by multiplying, and that is exactly why so many tools get it wrong. Length, mass and volume are proportional: twice the metres is twice the feet, and zero is zero on both scales. Temperature is not: 0 °C is not 0 °F, it is 32 °F, because each scale put its zero somewhere different.
The formula therefore has two parts, a factor and an offset: °F = °C × 9/5 + 32. A converter that applies only the factor will tell you 0 °C is 0 °F, and that 20 °C is 36 °F instead of 68. The flaw shows up worst in chained conversions: going from Fahrenheit to Rankine and on to Réaumur requires honouring each scale's offset at every step, and that is where the error piles up.
There is one neat point where the two main scales meet: −40 degrees. −40 °C is exactly −40 °F, and it is the only temperature where that happens. Kelvin, on the other hand, is proportional to Rankine, because both start at absolute zero: 0 K = 0 °R = −273.15 °C. That is also why kelvin carries no degree symbol.
Every unit in this category
Frequently asked questions
What is the Celsius to Fahrenheit formula?
°F = °C × 9/5 + 32. And back the other way, °C = (°F − 32) × 5/9. That “+32” is what many tools leave out.
Why isn't 0 °C equal to 0 °F?
Because the two scales picked their zeros in different places: Celsius at the freezing point of water, Fahrenheit at a salt-and-ice mixture that was colder still. The gap between those two zeros is precisely that “+32”.
At what temperature do Celsius and Fahrenheit agree?
At −40 degrees, and only there. It is a good quick test of whether a converter is built properly: if it gives you anything other than −40, do not use it.
Why does kelvin have no degree sign?
Because it is not a relative scale but an absolute one: it starts at absolute zero, the lowest possible temperature. You say “300 kelvin”, not “300 degrees kelvin”.