The formulas
Temperature scales differ by both a scale factor and an offset, so they cannot be converted with a single multiplication the way lengths can. This tool converts through Celsius:
- Celsius to Fahrenheit: °F = °C × 9/5 + 32
- Fahrenheit to Celsius: °C = (°F − 32) × 5/9
- Celsius to Kelvin: K = °C + 273.15
- Kelvin to Celsius: °C = K − 273.15
A conversion between Fahrenheit and Kelvin goes through Celsius in two steps. Treating temperature as a ratio would give wrong answers: 10 °C is 50 °F, not 18 °F.
Reference temperatures
Computed by the tool's own conversion engine:
| Point | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute zero | -273.15 °C | -459.67 °F | 0 K |
| Water freezes | 0 °C | 32 °F | 273.15 K |
| Same in °C and °F | -40 °C | -40 °F | 233.15 K |
| Typical room temperature | 20 °C | 68 °F | 293.15 K |
| Average human body temperature | 37 °C | 98.6 °F | 310.15 K |
| Water boils (at sea level) | 100 °C | 212 °F | 373.15 K |
Absolute zero
Nothing can be colder than absolute zero: 0 K, which is −273.15 °C or −459.67 °F. The tool rejects any input below absolute zero in whichever scale you enter it, because such a temperature does not exist. Ordinary negative temperatures, such as −20 °C on a winter day, are of course fine.
Where each scale is used
Celsius is the everyday scale in most of the world and in science. Fahrenheit remains common for weather and cooking in the United States. Kelvin is the SI unit of temperature and is used in physics, chemistry and engineering; it starts at absolute zero, so it has no negative values, and it is written without a degree sign.