The formula
°F = °C × 9/5 + 32. Multiply by 9/5 (that is, 1.8) because a Fahrenheit degree is smaller, then add 32 because water freezes at 32 °F, not 0. For 20 °C: 20 × 1.8 = 36, plus 32 is 68 °F. There is no single factor, which is why 10 °C is 50 °F but 20 °C is 68 °F, not 100.
Worked examples
Rounded to one decimal place:
| Celsius | Fahrenheit |
|---|---|
| −40 °C | −40 °F |
| −10 °C | 14 °F |
| 0 °C | 32 °F |
| 10 °C | 50 °F |
| 20 °C | 68 °F |
| 25 °C | 77 °F |
| 30 °C | 86 °F |
| 37 °C | 98.6 °F |
| 100 °C | 212 °F |
| 180 °C | 356 °F |
An oven at 180 °C is at 356 °F; recipes usually round that to 350 °F.
A quick estimate
Double the Celsius and add 30: 15 °C gives 60 against the real 59 °F. It is exact at 10 °C and drifts the hotter or colder it gets: at 35 °C it says 100 where the real answer is 95.
Questions
What is 37 °C in Fahrenheit?
98.6 °F, the figure usually given for normal body temperature. A fever is generally taken as 38 °C, which is 100.4 °F.
Is centigrade the same as Celsius?
Yes. Centigrade was the scale's older name; Celsius has been its official name since 1948.