Kelvin to Celsius (K to °C) Converter

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Kelvin to Celsius — Formula & Reference

Kelvin (K) is the SI base unit for thermodynamic temperature. Zero Kelvin (0 K) is absolute zero. Everyday temperatures in Celsius are obtained by subtracting 273.15 from the Kelvin value.

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Related Converters

Kelvin to Celsius — Science to Everyday Life

Kelvin is used throughout scientific literature, but everyday life uses Celsius or Fahrenheit. Converting is trivial: °C = K − 273.15. The surface of the Sun is about 5,778 K = 5,505 °C. Liquid nitrogen boils at 77 K = −196 °C. Human body temperature is 310 K = 36.85 °C. The cosmic microwave background — the coldest natural temperature in the observable universe — is 2.725 K = −270.42 °C, just barely above absolute zero.

Converting Kelvin to Celsius

The conversion from Kelvin to Celsius is °C = K − 273.15. The Kelvin and Celsius scales have identical degree sizes — a temperature difference of 1 K equals a difference of 1°C. Only the zero points differ: 0 K (absolute zero) = −273.15°C; 273.15 K = 0°C (water's freezing point); 373.15 K = 100°C (water's boiling point). Triple point of water: 273.16 K = 0.01°C.

Kelvin is used in scientific equations — the ideal gas law (PV = nRT), Stefan–Boltzmann law, and Planck's radiation law all require Kelvin. Experimental results in thermodynamics and chemistry are often reported in Kelvin; converting to Celsius makes them intuitive for practical applications. Cryogenic temperatures: liquid helium boils at 4.2 K (−268.95°C); liquid nitrogen at 77 K (−196.15°C).

Kelvin to Celsius Reference

Why Kelvin and Celsius Share the Same Degree Size

The Celsius and Kelvin scales are identical in their degree size — one kelvin equals exactly one degree Celsius in terms of interval. The only difference is their zero points: 0 K is absolute zero (−273.15°C), while 0°C is the freezing point of water. Converting between them requires only addition or subtraction: °C = K − 273.15. This equivalence means that temperature differences (ΔT) calculate identically in both scales. However, equations requiring absolute temperature magnitude — such as the ideal gas law PV = nRT or Wien’s displacement law — require Kelvin, because a Celsius temperature of −10° would produce invalid negative results in those formulas. Spectroscopy, astrophysics, and cryogenics routinely report in Kelvin while everyday lab measurements use Celsius, making this the most frequent temperature-scale conversion in scientific work.

Kelvin to Celsius Reference Table