Celsius to Kelvin Conversion
Also known as C to K · K to C · kelvin to celsius · celsius to kelvin formula · add 273.15 · absolute temperature from celsius
Units aren’t used in this calculation — every value is a plain number.
Worked example: 25 C → 298.15 K — press Try an example to run it live, then adjust anything.
Enter your known values, leave one input blank, and solves for the missing one. Tap a variable’s symbol to see what it means, with a typical value.
Learning zone
The kelvin scale keeps the Celsius degree and moves the zero. Its zero is absolute zero, the point at which a system has the least energy it can have, so a kelvin temperature is never negative and the scale has a true origin: 300 K really is twice 150 K in a way that 30 °C is not twice 15 °C.
That property is the entire reason the conversion is not optional. Every gas law divides by absolute temperature. The combined gas law, the ideal gas law, Charles's law, an isentropic ratio, a Carnot efficiency — all of them are wrong by an unbounded factor if a Celsius reading is fed in. Dividing by 0 °C is not the same operation as dividing by 273.15 K, and the failure is silent: the arithmetic completes and returns a plausible-looking number.
Two small precisions. The offset is 273.15, not 273 — the round number is a schoolroom shortcut that costs 0.15 K, which is more than the whole precision of many thermocouples. And there is no degree sign on a kelvin and no plural s in the symbol: 298.15 K, written that way, since the 1967 redefinition dropped "degrees Kelvin" from the SI. Because the degree size is unchanged, an interval needs no conversion at all: a rise of 10 K is a rise of 10 C°, exactly.
- = Celsius reading (°C)
- = Kelvin reading (K)
- Celsius reading — Celsius to Fahrenheit Conversion, Percent of a Number
- Kelvin reading — Celsius to Fahrenheit Conversion, Percent of a Number