Celsius to Fahrenheit, the quick way
The exact formula, a mental shortcut that gets you close, and the temperatures worth remembering.
Celsius and Fahrenheit do not just use different numbers. They also start in different places: water freezes at 0 °C but at 32 °F. That is why you can never convert by multiplying alone.
The exact formula
- °F = °C × 9 ÷ 5 + 32
- °C = (°F − 32) × 5 ÷ 9
A shortcut for the weather
Double the Celsius figure and add 30. At 20 °C that gives 70 °F against an exact 68 °F, so it stays within a few degrees across everyday weather. For cooking or anything medical, use the exact formula.
Temperatures worth remembering
| Celsius | Fahrenheit | What it is |
|---|---|---|
| −40 °C | −40 °F | Where the two scales meet |
| 0 °C | 32 °F | Water freezes |
| 20 °C | 68 °F | A comfortable room |
| 37 °C | 98.6 °F | Typical body temperature |
| 100 °C | 212 °F | Water boils at sea level |
Scientists add a third scale, Kelvin, which starts at absolute zero: K = °C + 273.15.
Try it yourself