Three temperature scales
Fahrenheit, Celsius and Kelvin describe the same physical temperature with different reference points. On the Celsius scale water freezes at 0 and boils at 100. The Fahrenheit scale, still used in the United States, sets those points at 32 and 212. Kelvin, the scientific scale, uses the same step size as Celsius but starts at absolute zero, so it has no negative values.
The formulas
Because each scale has its own zero, converting takes a shift and a change of scale, not just a multiplication:
- °F = °C × 1.8 + 32
- °C = (°F − 32) ÷ 1.8
- K = °C + 273.15
- K = (°F + 459.67) ÷ 1.8
A difference in temperature converts more simply. A rise of 10 °C is a rise of 18 °F and of 10 K, since only the scale factor applies to a difference.
How to use this converter
Type a value in any of the three fields and the other two update immediately. Negative temperatures work too: type a minus sign before the number. The pages linked below the converter give a full chart for each direction, handy to print for the kitchen or a weather trip abroad.
Reference temperatures
| Situation | °F | °C | K |
|---|---|---|---|
| Absolute zero | −459.67 | −273.15 | 0 |
| Scales are equal | −40 | −40 | 233.15 |
| Water freezes | 32 | 0 | 273.15 |
| Comfortable room | 68 | 20 | 293.15 |
| Normal body temperature | 98.6 | 37 | 310.15 |
| Water boils at sea level | 212 | 100 | 373.15 |
| Moderate oven | 350 | 176.7 | 449.8 |
Tips
Oven temperatures are usually rounded to the nearest 5 or 10 degrees when recipes are translated, so 350 °F becomes 180 °C rather than 176.7 °C. For fever thresholds, stay precise: 100.4 °F is exactly 38 °C.
The units in detail
What is a degree Celsius?
The Celsius scale puts the freezing point of water at 0 °C and its boiling point at sea level at 100 °C. It is the temperature scale of almost every country outside the US, of science and of medicine. A change of one degree Celsius equals a change of one kelvin.
What is a degree Fahrenheit?
On the Fahrenheit scale, water freezes at 32 °F and boils at 212 °F, so 180 degrees separate the two points instead of 100. The United States uses it for weather, ovens and body temperature, where 98.6 °F is the classic normal value.
What is a kelvin?
The kelvin is the SI unit of temperature. Its zero is absolute zero, the coldest possible temperature, and its steps are the same size as Celsius degrees, so 0 °C is 273.15 K. It is written without a degree sign and is used in physics, lighting color temperature and astronomy.