Convert Celsius to Fahrenheit
Fahrenheit = Celsius × 1.8 + 32. Type any temperature below to convert celsius to fahrenheit both ways — it runs entirely in your browser.
Celsius to Fahrenheit formula
Temperature scales have different zero points, so the conversion is a multiply-and-add, not a single ratio:
Fahrenheit = Celsius × 1.8 + 32
To go the other way, Celsius = Fahrenheit × 0.5555556 − 17.77778.
Worked example
Convert 25 °C to fahrenheit:
= 25 × 1.8 + 32 = 77 °F.
Common temperatures in Celsius and Fahrenheit
| Reference point | Celsius (°C) | Fahrenheit (°F) |
|---|---|---|
| Absolute zero | -273.15 | -459.67 |
| Freezing point of water | 0 | 32 |
| Refrigerator | 4 | 39.2 |
| Room temperature | 21 | 69.8 |
| Normal human body temperature | 37 | 98.6 |
| A hot summer day | 45 | 113 |
| Boiling point of water (sea level) | 100 | 212 |
About the Celsius and Fahrenheit scales
Celsius: Celsius (centigrade) puts 0° at the freezing point of water and 100° at its boiling point at sea level. It is the everyday temperature scale used almost everywhere outside the United States.
Fahrenheit: Fahrenheit puts water’s freezing point at 32° and its boiling point at 212° — a 180-degree span. It is the everyday scale in the United States and a few other territories.
Sources
- NIST Special Publication 811 — Guide for the Use of the SI — publishes the defining relations between the temperature scales. Unlike every other conversion on this site these are affine, not a single multiplying factor: t/°C = (t/°F − 32)/1.8 and T/K = (T/°R)/1.8 are exact by definition, so the figures here are exact rather than rounded — the scales simply have different zero points as well as different degree sizes.
- BIPM — The International System of Units (SI Brochure) — the defining document for the SI, published by the International Bureau of Weights and Measures. It fixes the base unit that this conversion resolves to, which is why the factor here can be exact rather than approximate.
Frequently asked questions
- What is 25 °C in Fahrenheit?
- 25 °C = 77 °F.
- How do I convert Celsius to Fahrenheit?
- Use fahrenheit = celsius × 1.8 + 32. For example, 25 °C → 77 °F.
- How do I convert Fahrenheit back to Celsius?
- Reverse it: celsius = fahrenheit × 0.5555556 − 17.77778.
- Why isn't converting Celsius to Fahrenheit just multiplication?
- Because the two scales start their zero at different temperatures, so after scaling by 1.8 you also add 32. Skipping that constant is the most common temperature-conversion mistake.