Converters Fahrenheit to Celsius
Convert °F to °C with the formula shown, plus oven temperatures, body temperature and a weather reference chart.
1 °F = -17.2222222222 °C
°C = (°F − 32) × 5/9
degrees Fahrenheit to degrees Celsius
| °F | °C |
|---|---|
| -40 | -40 |
| -20 | -28.888889 |
| -10 | -23.333333 |
| 0 | -17.777778 |
| 10 | -12.222222 |
| 20 | -6.666667 |
| 25 | -3.888889 |
| 30 | -1.111111 |
| 37 | 2.777778 |
| 40 | 4.444444 |
| 50 | 10 |
| 75 | 23.888889 |
| 100 | 37.777778 |
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Cite this page
Reembun. (2026, July 28). Fahrenheit to Celsius. https://reembun.com/convert/temperature/fahrenheit-to-celsius
How to use it
Type the Fahrenheit value
The Celsius figure appears as you type.
Go the other way
Swap units converts Celsius back into Fahrenheit.
Check the arithmetic
Subtract 32 first, then divide by 1.8. Doing those two the wrong way round is the usual reason a mental conversion comes out wrong.
The formulas
°C = (°F − 32) × 5/9
°F = (°C × 9/5) + 32Subtract before multiplying. Temperature scales are affine rather than proportional, with different zero points, so the offset must be removed before the ratio is applied.
The 5/9 ratio exists because a Fahrenheit degree is smaller: there are 180 Fahrenheit degrees between the freezing and boiling points of water, against 100 Celsius degrees.
Weather reference
| °F | °C | Feels like |
|---|---|---|
| 0 | −17.8 | Severe cold |
| 32 | 0 | Freezing |
| 50 | 10 | Cool |
| 60 | 15.6 | Mild |
| 68 | 20 | Comfortable room |
| 72 | 22.2 | Warm room |
| 80 | 26.7 | Warm day |
| 90 | 32.2 | Hot |
| 100 | 37.8 | Very hot |
| 110 | 43.3 | Dangerous |
Oven temperatures
| °F | °C | Gas mark | Use |
|---|---|---|---|
| 275 | 140 | 1 | Slow cooking |
| 325 | 160 | 3 | Rich fruit cake |
| 350 | 175 | 4 | Most baking |
| 375 | 190 | 5 | Pastry |
| 400 | 200 | 6 | Roasting |
| 425 | 220 | 7 | Hot roasting |
| 475 | 245 | 9 | Pizza, bread |
Recipes round to convenient numbers rather than converting exactly. A recipe calling for 350°F and one calling for 180°C are treated as the same oven setting, even though 350°F is 176.7°C. Fan ovens are conventionally set 20°C lower than the stated conventional temperature.
Body temperature
| °F | °C | Meaning |
|---|---|---|
| 95.0 | 35.0 | Hypothermia threshold |
| 97.9 | 36.6 | Modern average |
| 98.6 | 37.0 | Traditional “normal” |
| 100.4 | 38.0 | Fever |
| 103.0 | 39.4 | High fever |
| 104.0 | 40.0 | Seek medical advice |
The familiar 98.6 is 37.0°C converted to one decimal place. Its apparent precision is a conversion artefact rather than a measurement, and modern studies put the average closer to 36.6°C with substantial variation by individual, time of day and measurement site.
Mental arithmetic
°F → °C: subtract 30, then halve. 70°F → 40 ÷ 2 = 20°C. (True: 21.1)
°C → °F: double, then add 30. 20°C → 40 + 30 = 70°F. (True: 68)
Both stay within about 2 degrees between roughly −5°C and 30°C, which covers most weather. They drift at the extremes, so use the exact formula for anything that matters.
Common questions
What is the formula?
°C = (°F − 32) × 5/9. Subtract first, then multiply, because the two scales have different zero points, so the offset has to be removed before the ratio is applied. Doing it the other way round gives an answer that is wrong by about 18 degrees.
How do I estimate it quickly?
Subtract 30 and halve. For 70°F that gives 20°C against a true 21.1°C. The approximation is within about 2 degrees across normal weather temperatures and drifts further at the extremes.
What temperature is the same in both scales?
Minus 40. It is the only crossing point, since −40°C = −40°F. Setting x = (x − 32) × 5/9 and solving gives exactly that.
Why is normal body temperature 98.6°F?
Because it is 37°C converted precisely. The 37 came from Carl Wunderlich's 1868 study, and the apparent precision of 98.6 is an artefact of the conversion. Modern research puts the average nearer 36.6°C, or 97.9°F.
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