Kelvin to Celsius conversion

Kelvin to Celsius

Temperatures in scientific papers, data sheets and astronomy articles are given in kelvin, the SI unit whose zero is absolute zero. To turn them into the familiar Celsius scale, subtract 273.15: °C = K − 273.15. Nothing else changes, because a kelvin and a degree Celsius are the same size.

Typical values

• 0 K = −273.15 °C (absolute zero)
• 77 K = −196.15 °C (liquid nitrogen)
• 195 K = −78.15 °C (dry ice)
• 273.15 K = 0 °C (ice melts)
• 293.15 K = 20 °C (room temperature)
• 300 K = 26.85 °C (a common "round" value in physics problems)
• 310.15 K = 37 °C (body temperature)
• 373.15 K = 100 °C (water boils)
• 1000 K = 726.85 °C

Reading kelvin values in everyday contexts

Light bulbs and screens. Colour temperature in kelvin is not a temperature you can feel; 2700 K describes the warm colour of an incandescent bulb, 6500 K the bluish white of daylight. Converting these to Celsius is mathematically valid (2700 K = 2427 °C) but meaningless for choosing a lamp.

Weather and climate science. Global temperature datasets are often stored in kelvin to avoid negative numbers. A monthly mean of 288 K is 14.85 °C — close to the Earth's average surface temperature.

Cryogenics. Liquid helium boils at 4.2 K, which is −268.95 °C. At these temperatures Celsius numbers become clumsy, which is exactly why kelvin exists.

Common mistakes

Do not write "°K" — the unit is just K. And remember that differences are the same in both scales: a rise of 10 K is a rise of 10 °C, with no 273.15 involved.

Worked examples

A star's surface at 5 800 K. 5 800 − 273.15 = 5 527 °C — the Sun.

A 3 000 K light bulb. The filament really is at about 2 727 °C; the "warm white" colour is a side effect of that temperature.

Liquid oxygen at 90 K. 90 − 273.15 = −183.15 °C.

Frequently asked questions

What is 0 K in Celsius? −273.15 °C, absolute zero.

What is 298 K? 24.85 °C — the "standard ambient temperature" used in thermodynamics tables.

Why does chemistry use kelvin? Because gas laws and reaction-rate equations need a temperature that is proportional to molecular energy; Celsius has an arbitrary zero and would give wrong ratios.

Related conversions

To reach Fahrenheit, convert to Celsius first and then use Celsius to Fahrenheit: 300 K → 26.85 °C → 80.3 °F.

Good to know

In weather and climate data, kelvin values look odd only because of the offset: a global mean of 288 K is a comfortable 14.85 °C, and a warming of 1.5 K is exactly 1.5 °C — temperature differences are identical in the two scales. Satellite instruments report sea-surface and cloud-top temperatures in kelvin; meteorologists convert for the public. In engineering, the "kelvin" you see on a thermal-resistance spec (K/W) is again a difference, not an absolute temperature, so no 273.15 is involved. Only when a single absolute value is quoted — the boiling point of nitrogen at 77 K, the surface of Venus at 737 K — does the subtraction apply.