A US recipe says 350°F. A weather app abroad says 28°C. A thermometer reads 100.4°F. Converting between Celsius and Fahrenheit is one of those things you need just often enough to forget how.
The formulas
Celsius to Fahrenheit: °F = °C × 9/5 + 32
Fahrenheit to Celsius: °C = (°F − 32) × 5/9
9/5 is the same as 1.8, so you can also write °F = °C × 1.8 + 32.
Worked examples
- 25°C to °F: 25 × 1.8 = 45, + 32 = 77°F.
- 350°F to °C: 350 − 32 = 318, × 5/9 = 176.7°C (recipes round it to 180°C).
- 98.6°F to °C: 98.6 − 32 = 66.6, × 5/9 = 37°C.
The quick mental shortcut
For weather-range temperatures:
- °C to °F: double it and add 30. 20°C → 40 + 30 = 70°F (actual: 68°F).
- °F to °C: subtract 30 and halve it. 80°F → 50 ÷ 2 = 25°C (actual: 26.7°C).
It drifts at the extremes, so use the exact formula for cooking or medicine.
Everyday temperature chart
| Celsius | Fahrenheit | What it means |
|---|---|---|
| −40°C | −40°F | Where the two scales meet |
| −18°C | 0°F | Freezer |
| 0°C | 32°F | Water freezes |
| 4°C | 39°F | Fridge |
| 20°C | 68°F | Room temperature |
| 30°C | 86°F | Hot day |
| 37°C | 98.6°F | Normal body temperature |
| 38°C | 100.4°F | Fever threshold |
| 100°C | 212°F | Water boils at sea level |
Common oven temperatures
| Celsius | Fahrenheit |
|---|---|
| 150°C | 300°F |
| 160°C | 325°F |
| 180°C | 350°F |
| 190°C | 375°F |
| 200°C | 400°F |
| 220°C | 425°F |
Recipes round these to the nearest 25°F, so small differences won't change the result. Fan ovens usually run about 20°C cooler than the recipe's conventional-oven setting.
What about Kelvin?
Kelvin is the scientific scale that starts at absolute zero. K = °C + 273.15, so 0°C is 273.15 K. There's no degree sign — it's just "kelvin".
Convert instantly
- Open the free Unit Converter.
- Choose Temperature.
- Pick Celsius, Fahrenheit or Kelvin on each side and type a value — the result updates as you type.
FAQ
Why does the US use Fahrenheit? It was the standard in the British Empire when the US adopted its units, and the US never switched to metric for everyday use.
Is there a temperature that's the same in both? Yes, −40°.
Try it now
Convert any temperature with the free Unit Converter.
Related reading
See Everyday Unit Conversions Made Simple and How to Convert Kilograms to Pounds.