Kelvin to Celsius Converter

Subtract 273.15 from the kelvin value. Nothing gets multiplied, since one kelvin is exactly as large as one Celsius degree; the scales are just shifted.

For 77 K, a common figure in cryogenics: 77 − 273.15 = −196.15 °C. For a hot filament at 1,000 K: 1,000 − 273.15 = 726.85 °C. Any value under 273.15 K comes out below zero Celsius.

The same subtraction works for colour temperature written in kelvins, although there the number describes the hue of a light source rather than how hot anything feels.

Take away 273, or 270 if you only need a rough idea. 310 K becomes about 37 °C (exactly 36.85), body temperature. Above a few thousand kelvins the offset hardly matters: 5,772 K is 5,499 °C, so “about 5,500” is a fair reading.

Near the bottom of the scale the reverse is true and the offset is almost all of the answer. Liquid helium at 4.2 K is −268.95 °C: a reading that looks tiny in kelvins sits just a few degrees above the coldest point physics allows, which is why low-temperature work is almost always reported in kelvins.