Temperature Converter
Convert temperatures between Celsius, Fahrenheit and Kelvin with the exact formulas.
Temperature formulas
Unlike length or weight, temperature scales have different zero points, so you cannot convert with a single multiplier.
°F = °C × 9/5 + 32 °C = (°F − 32) × 5/9 K = °C + 273.15
25 °C × 1.8 + 32 = 77 °F. And 98.6 °F: (98.6 − 32) × 5/9 = 37 °C.
Reference temperatures
| °C | °F | K | |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Celsius equals Fahrenheit | −40 | −40 | 233.15 |
| Water freezes | 0 | 32 | 273.15 |
| Room temperature | 20–22 | 68–72 | 293–295 |
| Body temperature | 37 | 98.6 | 310.15 |
| Water boils (sea level) | 100 | 212 | 373.15 |
| Moderate oven | 180 | 356 | 453.15 |
Quick mental conversion
To estimate °F from °C, double it and add 30. 20 °C becomes about 70 °F (exact: 68 °F). To go back, subtract 30 and halve. The shortcut is closest between about 0 and 30 °C.
About Kelvin
Kelvin is the SI unit of temperature, used in science. It starts at absolute zero, the coldest possible temperature, and uses the same step size as Celsius. Kelvin is written without a degree sign: 300 K, not 300 °K.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 (or 1.8) and add 32. For example, 30 °C is 30 × 1.8 + 32 = 86 °F.
At what temperature are Celsius and Fahrenheit equal?
At −40 degrees. −40 °C is exactly −40 °F.
What is a fever in Celsius?
A temperature of 38 °C (100.4 °F) or higher is generally considered a fever in adults.
Last reviewed Oct 20, 2026. Results are estimates; check important decisions with a qualified professional.