Kelvin to Celsius

Kelvins and degrees Celsius

The kelvin is the SI base unit of thermodynamic temperature, starting at absolute zero; since 2019 it is defined by fixing the Boltzmann constant. Science and engineering use kelvins, as do color temperatures of light bulbs and screens (2700 K warm, 6500 K daylight).

The Celsius scale is defined from the kelvin: t/°C = T/K − 273.15, so water freezes at about 0 °C and boils at about 100 °C at sea level. Weather, cooking and body temperature are given in Celsius almost everywhere except the United States.

Worked example

Convert 300 K with °C = K − 273.15: the result is 26.85 °C. Likewise 293.15 K = 20 °C.

Estimating in your head

Subtract 273, or 273.15 for exact work: 300 K is about 27 °C.

Going the other way

To convert degrees Celsius to kelvins, type in the right-hand box; the page solves the same formula backwards. The swap button between the boxes opens the reverse page.

°C = K − 273.15

Temperature scales have different zero points as well as different degree sizes, so the conversion scales and shifts; there is no single factor. The page converts through kelvin using the exact definitions in NIST SP 811. Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.