Fahrenheit to Celsius
Convert Fahrenheit to Celsius. Subtract 32 and multiply by 5/9, with reference tables for weather, body temperature and oven settings.
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The formula
celsius = (fahrenheit − 32) × 5/9Temperature is the one conversion on this site that is not a multiplication. The two scales have different zero points as well as different step sizes, so the 32 has to come off before the scaling. Multiplying by 5/9 alone gives a wrong answer at every temperature except −40.
To go the other way, multiply by 9/5 and add 32. See Celsius to Fahrenheit.
Quick reference
| Fahrenheit | Celsius | |
|---|---|---|
| −40 °F | −40 °C | the scales cross here |
| 0 °F | −17.8 °C | |
| 32 °F | 0 °C | water freezes |
| 50 °F | 10 °C | |
| 68 °F | 20 °C | room temperature |
| 72 °F | 22.2 °C | a common thermostat setting |
| 86 °F | 30 °C | |
| 98.6 °F | 37 °C | body temperature |
| 212 °F | 100 °C | water boils at sea level |
Weather
| Fahrenheit | Celsius | Feels like |
|---|---|---|
| 0 °F | −17.8 °C | severe cold |
| 20 °F | −6.7 °C | hard frost |
| 32 °F | 0 °C | freezing |
| 45 °F | 7.2 °C | cold |
| 60 °F | 15.6 °C | mild |
| 75 °F | 23.9 °C | warm |
| 85 °F | 29.4 °C | hot |
| 95 °F | 35 °C | very hot |
| 105 °F | 40.6 °C | dangerous |
A useful landmark: the two scales agree on how hot “hot” sounds at 28 °C and 82 °F, which are close but not equal — 28 °C is 82.4 °F.
Body temperature
The famous 98.6 °F is a conversion artefact. The original nineteenth-century measurement was 37 °C, stated to two significant figures. Converting 37 exactly gives 98.6, which was then read as a precise figure in its own right and reported to three. Normal body temperature is a range of roughly 36.1–37.2 °C (97–99 °F), not a single number.
| Fahrenheit | Celsius | |
|---|---|---|
| 97.0 °F | 36.1 °C | low end of normal |
| 98.6 °F | 37.0 °C | the traditional figure |
| 100.4 °F | 38.0 °C | usual threshold for a fever |
| 102.2 °F | 39.0 °C | high fever |
| 104.0 °F | 40.0 °C | seek help |
Oven temperatures
Recipes round oven settings to whatever is a whole number on their own scale, so the two columns rarely match exactly:
| Fahrenheit | Celsius | Gas mark |
|---|---|---|
| 275 °F | 135 °C | 1 |
| 325 °F | 163 °C | 3 |
| 350 °F | 177 °C | 4 |
| 375 °F | 191 °C | 5 |
| 400 °F | 204 °C | 6 |
| 425 °F | 218 °C | 7 |
| 450 °F | 232 °C | 8 |
British and European recipes usually give a rounded Celsius figure — 180 °C for 350 °F — and subtract about 20 °C for a fan oven.
Estimating in your head
Subtract 30, then halve. 75 °F − 30 = 45, halved is 22.5 °C against a true 23.9 °C. The method runs a degree or two low in the ordinary weather range and gets worse the further you go from it, but it is close enough to decide what to wear.