Convert Fahrenheit to Celsius
Celsius = Fahrenheit × 0.5555556 − 17.77778. Type any temperature below to convert fahrenheit to celsius both ways — it runs entirely in your browser.
Fahrenheit to Celsius formula
Temperature scales have different zero points, so the conversion is a multiply-and-add, not a single ratio:
Celsius = Fahrenheit × 0.5555556 − 17.77778
To go the other way, Fahrenheit = Celsius × 1.8 + 32.
Worked example
Convert 98.6 °F to celsius:
= 98.6 × 0.5555556 − 17.77778 = 37 °C.
Common temperatures in Fahrenheit and Celsius
| Reference point | Fahrenheit (°F) | Celsius (°C) |
|---|---|---|
| Absolute zero | -459.67 | -273.15 |
| Freezing point of water | 32 | 0 |
| Refrigerator | 39.2 | 4 |
| Room temperature | 69.8 | 21 |
| Normal human body temperature | 98.6 | 37 |
| A hot summer day | 113 | 45 |
| Boiling point of water (sea level) | 212 | 100 |
About the Fahrenheit and Celsius scales
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.
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.
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 98.6 °F in Celsius?
- 98.6 °F = 37 °C.
- How do I convert Fahrenheit to Celsius?
- Use celsius = fahrenheit × 0.5555556 − 17.77778. For example, 98.6 °F → 37 °C.
- How do I convert Celsius back to Fahrenheit?
- Reverse it: fahrenheit = celsius × 1.8 + 32.
- Why isn't converting Fahrenheit to Celsius just multiplication?
- Because the two scales start their zero at different temperatures, so after scaling by 0.5555556 you also subtract 17.77778. Skipping that constant is the most common temperature-conversion mistake.