Convert KELVIN to CELSIUS, Free
Type any KELVIN value and see the CELSIUS result instantly. No button press needed.
How to convert KELVIN to CELSIUS
Kelvin and Celsius use the same size degree: a change of 1 K is identical to a change of 1 degree C. The only difference is where zero is placed. Celsius defines 0 as the freezing point of water; Kelvin defines 0 as absolute zero, the coldest theoretically possible temperature, which sits at -273.15 degrees C. To convert Kelvin to Celsius, subtract 273.15: C = K - 273.15. The calculation runs instantly in your browser as pure JavaScript arithmetic.
Kelvin is used exclusively in scientific and engineering contexts where absolute temperature is needed: thermodynamics, astrophysics, color temperature of light sources, and cryogenics. Human body temperature is about 310 K. The surface of the sun is roughly 5778 K. Liquid nitrogen boils at 77 K (-196 C). Room temperature is around 293-298 K (20-25 C). For everyday weather and cooking, Celsius is the practical unit; Kelvin values are used when calculations require an absolute baseline, like computing gas pressures or color temperature of lighting.
Enter the Kelvin value
Type a temperature in Kelvin. Values below 0 K are physically impossible; the tool flags these as invalid.
Read the Celsius result
The result appears instantly: K - 273.15 = degrees Celsius. For example, 300 K = 26.85 C.
Convert Fahrenheit too if needed
The page also shows the Fahrenheit equivalent for completeness: (K - 273.15) x 9/5 + 32.
Reverse the conversion
To go from Celsius to Kelvin, add 273.15. Enter a Celsius value in the reverse field to confirm.
Frequently asked questions
What is the formula to convert Kelvin to Celsius?
Celsius = Kelvin - 273.15. This is exact by definition.
What is 0 Kelvin in Celsius?
-273.15 degrees Celsius. This is absolute zero, the lowest possible temperature.
What is room temperature in Kelvin?
Standard room temperature is defined as 293.15 K (20 C) or 298.15 K (25 C) depending on the context.
Why is Kelvin used in science instead of Celsius?
Many physical laws (ideal gas law, Stefan-Boltzmann law, Planck's radiation law) require an absolute temperature scale. Kelvin starts at the true zero point, making equations work correctly without negative values or offset constants.
What is 5778 K (sun surface temperature) in Celsius?
5778 - 273.15 = 5504.85 degrees Celsius.