Unit converter
Celsius to Fahrenheit.
Convert °C to °F and °F to °C. Type in either box and the other follows. Temperature scales have different zero points, so this conversion is a stretch and a shift — which is why it needs a formula rather than a single multiplier.
| °C | °F |
|---|---|
| −40 °C | −40 °F |
| −20 °C | −4 °F |
| −10 °C | 14 °F |
| 0 °C | 32 °F |
| 5 °C | 41 °F |
| 10 °C | 50 °F |
| 15 °C | 59 °F |
| 20 °C | 68 °F |
| 25 °C | 77 °F |
| 30 °C | 86 °F |
| 37 °C | 98.6 °F |
| 40 °C | 104 °F |
| 50 °C | 122 °F |
| 75 °C | 167 °F |
| 100 °C | 212 °F |
- C Celsius · F Fahrenheit · K kelvin (SI base unit) · the two scales cross at −40°
Definitions
- Both scales are defined against the kelvin, so the conversion is exact: 0 °C is exactly 273.15 K, and one Fahrenheit degree is exactly 5⁄9 of a kelvin.
- A temperature and a temperature change convert differently. A reading of 10 °C is 50 °F, but a rise of 10 °C is a rise of 18 °F — the offset applies to the reading, not to the interval.
- Kelvin takes no degree sign and no "degrees": it is written 298.15 K, not 298.15 °K.
- Absolute zero is 0 K = −273.15 °C = −459.67 °F. Values below it are physically meaningless; the converter will still calculate them, because it converts numbers and does not police your physics.
- Réaumur and Rankine are included for completeness. Rankine is Fahrenheit-sized degrees counted from absolute zero, used in some US engineering work.
How it works
To convert Celsius to Fahrenheit, multiply by 9/5 (that is, 1.8) and add 32. To convert Fahrenheit to Celsius, subtract 32 first, then multiply by 5/9. The order matters: the subtraction undoes the offset before the scaling, and doing it the other way round is the classic wrong answer.
The mental shortcut is to double and add 30: 20 °C gives roughly 70 °F against the true 68 °F. It is close enough for weather and wrong enough for anything else, which is why the exact formula is on the page.
Internally every temperature is converted to kelvin, the SI base unit, and back out to the unit you chose. Handling the scale factor and the offset separately is what lets kelvin, Rankine and Réaumur share one calculation with Celsius and Fahrenheit instead of each needing its own special case.
Common questions this answers: what 20 degrees C is in F (68 °F), what 100 °F is in Celsius (37.8 °C), normal body temperature (37 °C = 98.6 °F), a fan oven at 180 °C (356 °F), and the one temperature where the two scales agree (−40°).
- Free
- No ads
- No tracking
- No account
- Works offline once loaded
From the maker of Ans — a scientific calculator you can own. Same idea: a proper instrument, nothing in the way.