The formula
°C = K × 1 − 273.15
Where the factor comes from — each unit by its definition, then its size in SI:
1 K is the SI unit of temperature.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: 273.15 K = 0 °C — 273.15 × 1 − 273.15 = 0
- Human body temperature: 310.15 K = 37 °C — 310.15 × 1 − 273.15 = 37
- A baking oven (350 °F): 449.817 K = 176.667 °C — 449.817 × 1 − 273.15 = 176.667
- A warm room: 293.15 K = 20 °C — 293.15 × 1 − 273.15 = 20
Frequently asked questions
How many degrees Celsius is 1 K?
1 K = -272.15 °C. The rule is °C = K × 1 − 273.15.
How do I convert degrees Celsius back to kelvin?
Invert the rule: K = (°C − -273.15) / 1.