Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, and Rankine. Each conversion uses explicit forward and reverse formulas — never a simple scale factor — because temperature scales have both offsets and different unit sizes.
Quick Converter
Result
20 °C = 68 °F
°F = (°C × 9/5) + 32
About Temperature Scales
Temperature is unusual among physical quantities: there are four widely-used scales, each with a different zero point, and only one (Kelvin) starts at absolute zero. That makes temperature conversions fundamentally different from length or mass conversions, which are pure ratio conversions.
The four scales
- Celsius (°C) — 0 °C is the freezing point of water, 100 °C the boiling point at 1 atm. Used throughout the world, especially outside the US.
- Fahrenheit (°F) — 32 °F is the freezing point of water, 212 °F the boiling point. Used primarily in the US.
- Kelvin (K) — the SI base unit of thermodynamic temperature. 0 K is absolute zero. Unlike Celsius and Fahrenheit, Kelvin is an absolute scale: no degree symbol, and always non-negative.
- Rankine (°R) — an absolute scale based on Fahrenheit-sized degrees. 0 °R is absolute zero. Used in some US engineering fields.
The exact formulas
- °F = (°C × 9/5) + 32
- °C = (°F − 32) × 5/9
- K = °C + 273.15
- °C = K − 273.15
- °R = (°C + 273.15) × 9/5
- °R = °F + 459.67
These relationships are exact. The 273.15 offset between Celsius and Kelvin is exact by the current definition of the kelvin. The 32 °F offset and 9/5 ratio between Celsius and Fahrenheit are also exact by definition.