Degrees Fahrenheit to degrees Celsius (°F to °C)

The formula

°C = °F × 0.5555555556 − 17.77777778

Where the factor comes from — each unit by its definition, then its size in SI:

• T(K) = (T(°F) + 459.67) × 0.5555555556
• T(K) = (T(°C) + 273.15) × 1

Gas laws and radiation formulas need absolute temperature in kelvin. Celsius and kelvin differ by an offset only; Fahrenheit differs in both offset and step size, so it is a formula, not a single factor.

Worked examples

• Water freezing: 32 °F = 0 °C — 32 × 0.5555555556 − 17.77777778 = 0
• Human body temperature: 98.6 °F = 37 °C — 98.6 × 0.5555555556 − 17.77777778 = 37
• A baking oven: 350 °F = 176.667 °C — 350 × 0.5555555556 − 17.77777778 = 176.667
• A warm room (293.15 K): 68 °F = 20 °C — 68 × 0.5555555556 − 17.77777778 = 20

Frequently asked questions