How to convert Celsius to Fahrenheit
- Type a temperature in Celsius (°C): the Fahrenheit (°F) and Kelvin (K) boxes update straight away.
- To convert Fahrenheit to Celsius, type in the Fahrenheit box instead. Negative numbers work: type a minus sign first.
- Below the result you see the formula with your numbers, a quick mental estimate and, for well-known temperatures, what they mean.
The formulas
- °F = °C × 9/5 + 32 (9/5 is 1.8)
- °C = (°F − 32) × 5/9
- K = °C + 273.15, and °C = K − 273.15
The two scales differ in two ways: they start at different points (water freezes at 0 °C but 32 °F) and their degrees are different sizes (100 Celsius degrees span the same range as 180 Fahrenheit degrees, hence 180/100 = 9/5). That is why you multiply and add, rather than just multiply.
Worked examples: 37 °C × 1.8 = 66.6, plus 32 = 98.6 °F. 350 °F − 32 = 318, × 5/9 = 176.7 °C. And at −40 the two scales meet: −40 °C is exactly −40 °F.
Mental shortcuts
- Celsius to Fahrenheit: double it and add 30. 15 °C → 30 + 30 = 60 °F (exact: 59 °F). It is spot on at 10 °C and drifts further out the hotter or colder it gets.
- Fahrenheit to Celsius: subtract 30 and halve. 80 °F → 50 ÷ 2 = 25 °C (exact: 26.7 °C).
- For an exact answer in your head: double the Celsius figure, take away a tenth of that, then add 32. 20 °C → 40 − 4 + 32 = 68 °F.
- Memorable pairs: 16 °C ≈ 61 °F and 28 °C ≈ 82 °F (the digits swap), 10 °C = 50 °F, 30 °C = 86 °F.
Common temperatures
| Celsius | Fahrenheit | Kelvin | What it is |
|---|---|---|---|
| −40 °C | −40 °F | 233.15 K | Celsius and Fahrenheit are equal |
| −18 °C | −0.4 °F | 255.15 K | Domestic freezer (about 0 °F) |
| 0 °C | 32 °F | 273.15 K | Water freezes |
| 4 °C | 39.2 °F | 277.15 K | Fridge |
| 10 °C | 50 °F | 283.15 K | Cool day |
| 20 °C | 68 °F | 293.15 K | Room temperature |
| 25 °C | 77 °F | 298.15 K | Warm day |
| 30 °C | 86 °F | 303.15 K | Hot day |
| 37 °C | 98.6 °F | 310.15 K | Typical body temperature |
| 38 °C | 100.4 °F | 311.15 K | Fever (NHS: 38 °C or above) |
| 40 °C | 104 °F | 313.15 K | Very hot day |
| 60 °C | 140 °F | 333.15 K | Very hot water: scalds within seconds |
| 100 °C | 212 °F | 373.15 K | Water boils at sea level |
Normal body temperature varies from person to person and through the day; the NHS describes it as around 36 to 37 °C (96.8 to 98.6 °F), and a high temperature (fever) as 38 °C (100.4 °F) or above.
Celsius to Fahrenheit chart
| °C | °F | °C | °F |
|---|---|---|---|
| −30 °C | −22 °F | −25 °C | −13 °F |
| −20 °C | −4 °F | −15 °C | 5 °F |
| −10 °C | 14 °F | −5 °C | 23 °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 | 35 °C | 95 °F |
| 40 °C | 104 °F | 50 °C | 122 °F |
| 60 °C | 140 °F | 70 °C | 158 °F |
| 80 °C | 176 °F | 90 °C | 194 °F |
| 100 °C | 212 °F |
Fahrenheit to Celsius chart
| °F | °C | °F | °C |
|---|---|---|---|
| 0 °F | −17.8 °C | 10 °F | −12.2 °C |
| 20 °F | −6.7 °C | 32 °F | 0 °C |
| 40 °F | 4.4 °C | 50 °F | 10 °C |
| 60 °F | 15.6 °C | 68 °F | 20 °C |
| 70 °F | 21.1 °C | 75 °F | 23.9 °C |
| 80 °F | 26.7 °C | 90 °F | 32.2 °C |
| 98.6 °F | 37 °C | 100 °F | 37.8 °C |
| 104 °F | 40 °C | 110 °F | 43.3 °C |
| 212 °F | 100 °C |
Oven temperatures: °F, °C and gas marks
Recipes round oven temperatures to convenient numbers, so the usual pairings are close to, but not exactly, the converted value. For a fan (convection) oven, recipes usually suggest about 20 °C lower.
| Gas mark | Recipe °F | Recipe °C | Exact °C for that °F |
|---|---|---|---|
| 1 | 275 °F | 140 °C | 135 °C |
| 2 | 300 °F | 150 °C | 148.9 °C |
| 3 | 325 °F | 170 °C | 162.8 °C |
| 4 | 350 °F | 180 °C | 176.7 °C |
| 5 | 375 °F | 190 °C | 190.6 °C |
| 6 | 400 °F | 200 °C | 204.4 °C |
| 7 | 425 °F | 220 °C | 218.3 °C |
| 8 | 450 °F | 230 °C | 232.2 °C |
| 9 | 475 °F | 240 °C | 246.1 °C |
Who uses which scale?
Celsius is used for everyday temperatures almost everywhere. Fahrenheit is still the everyday scale in the United States and a handful of other countries and territories, which is why weather apps, recipes and thermometers often need converting. Kelvin is the SI unit used in science: it starts at absolute zero (−273.15 °C), has degrees the same size as Celsius, and is written without a degree sign (300 K, not 300 °K).
The scales are named after their inventors: Daniel Gabriel Fahrenheit proposed his in 1724, and Anders Celsius proposed his in 1742, originally with 0 as the boiling point and 100 as freezing; it was turned the other way round soon after his death.
Converting lengths or weights too? Use the cm to inches converter and the kg to lbs converter, or read the guide to metric and imperial conversions. More quick helpers are in everyday tools.
Frequently asked questions
What is the formula for Celsius to Fahrenheit?
Multiply by 9/5 (1.8) and add 32: °F = °C × 1.8 + 32. For example 25 °C × 1.8 + 32 = 77 °F.
How do I convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9: °C = (°F − 32) × 5/9. For example (100 °F − 32) × 5/9 = 37.8 °C.
What is 37 °C in Fahrenheit?
98.6 °F, the figure often quoted as normal body temperature. In practice a healthy temperature is around 36 to 37 °C.
What is 350 °F in Celsius?
176.7 °C. Recipes round it to 180 °C (gas mark 4), or about 160 °C in a fan oven.
At what temperature are Celsius and Fahrenheit the same?
At −40. Solving C = C × 9/5 + 32 gives C = −40, so −40 °C and −40 °F are the same temperature.
How do I convert Celsius to kelvin?
Add 273.15. Room temperature of 20 °C is 293.15 K, and absolute zero, 0 K, is −273.15 °C or −459.67 °F.
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