Temperature Converter — Celsius, Fahrenheit, Kelvin & Rankine

Temperature conversion uses scale and offset

Temperature is not converted with a simple multiplier. Celsius and Fahrenheit have different zero points as well as different degree sizes, so the offset must be applied in the correct order. CalcOS converts through kelvin, the SI base unit of thermodynamic temperature.

°F = (°C × 9/5) + 32 · K = °C + 273.15

Using one canonical kelvin pathway also makes absolute-zero validation consistent across every pair.

Reference temperature points

Reference	Celsius	Fahrenheit	Kelvin
Absolute zero	−273.15 °C	−459.67 °F	0 K
Water freezing point*	0 °C	32 °F	273.15 K
Equal Celsius/Fahrenheit value	−40 °C	−40 °F	233.15 K
Water boiling point*	100 °C	212 °F	373.15 K

*Freezing and boiling reference values assume pure water at standard atmospheric pressure; real conditions vary with pressure and composition.

Temperature versus temperature interval

An absolute temperature and a temperature difference are different quantities. A change of 1 °C equals a change of 1 K, while a change of 1 °F equals 5/9 K. The +32 and 273.15 offsets apply to absolute readings, not to temperature intervals.

Why kelvin has no degree sign

The unit name is kelvin and its symbol is K, not “degree Kelvin” or °K. Celsius and Fahrenheit use the degree sign; kelvin does not.