The Celsius to Fahrenheit formula
Water freezes at 0°C, which is 32°F, and boils at 100°C, which is 212°F. So 100 Celsius degrees cover the same gap as 180 Fahrenheit degrees, and each degree Celsius is 1.8 (or 9/5) degrees Fahrenheit. That gives two simple formulas:
°F = °C × 9 ÷ 5 + 32
°C = (°F − 32) × 5 ÷ 9
Quick trick in your head: double the Celsius and add 30. 20°C becomes 40 + 30 = 70°F (the exact answer is 68°F). To go the other way, take 30 off the Fahrenheit and halve it. It's close enough for the weather, but use the calculator for cooking or medical temperatures.
Celsius used to be called centigrade in the UK. They're the same scale, so 20 degrees centigrade is 20°C.
Worked examples
What is 20°C in Fahrenheit?
20 × 9 = 180, ÷ 5 = 36, + 32 = 68°F. A comfortable room temperature.
What is 37°C in Fahrenheit?
37 × 9 ÷ 5 = 66.6, + 32 = 98.6°F, the traditional "normal" body temperature. The NHS says a temperature of 38°C (100.4°F) or above counts as a high temperature.
What is 350°F in Celsius?
350 − 32 = 318, × 5 = 1,590, ÷ 9 = 176.7°C. American recipes that say 350°F mean a moderate oven, which UK recipes write as 180°C or gas mark 4.
When are Celsius and Fahrenheit the same?
At −40. −40°C is exactly −40°F, the only temperature where the two scales meet.
Weather temperatures
| Celsius | Fahrenheit | What it feels like |
|---|---|---|
| −5°C | 23°F | Hard frost |
| 0°C | 32°F | Freezing point |
| 10°C | 50°F | Cool spring or autumn day |
| 15°C | 59°F | Mild |
| 20°C | 68°F | Warm, typical room temperature |
| 25°C | 77°F | A warm UK summer day |
| 30°C | 86°F | Hot |
| 40°C | 104°F | Extreme heat (the UK first passed 40°C in July 2022) |
Oven temperatures and gas marks
For a fan oven, turn the Celsius temperature down by about 20°C.
| Gas mark | °C | Fan °C | °F | Description |
|---|---|---|---|---|
| 1 | 140°C | 120°C | 275°F | Very low |
| 2 | 150°C | 130°C | 300°F | Low |
| 3 | 170°C | 150°C | 325°F | Moderately low |
| 4 | 180°C | 160°C | 350°F | Moderate |
| 5 | 190°C | 170°C | 375°F | Moderately hot |
| 6 | 200°C | 180°C | 400°F | Hot |
| 7 | 220°C | 200°C | 425°F | Hot |
| 8 | 230°C | 210°C | 450°F | Very hot |
| 9 | 240°C | 220°C | 475°F | Very hot |
The cooking conversion calculator also handles cups, ounces and grams, and the turkey cooking time calculator works out roasting times.
What about Kelvin?
Kelvin is the scientific scale. It uses the same size degree as Celsius but starts at absolute zero, the coldest possible temperature. To convert, add 273.15 to the Celsius figure, so 20°C is 293.15 K. Kelvin doesn't use a degree sign.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 9, divide by 5 and add 32. For example, 30°C × 9 ÷ 5 = 54, plus 32 = 86°F.
How do I convert Fahrenheit to Celsius?
Subtract 32, multiply by 5 and divide by 9. For example, (50°F − 32) × 5 ÷ 9 = 10°C.
What is 37°C in Fahrenheit?
37°C is 98.6°F. The NHS treats 38°C (100.4°F) or above as a high temperature.
What is 180°C in Fahrenheit?
180°C is 356°F. In recipes it is usually rounded to 350°F, which is gas mark 4.
At what temperature are Celsius and Fahrenheit equal?
At −40. −40°C is exactly the same as −40°F.
Last reviewed October 2026. Body temperature guidance is from the NHS. This is not medical advice.