Why you add 273 to convert celsius to kelvin?

Answer 1

The answer is 546.15 K (approx.). The Kelvin scale starts at absolute zero and is used in scientific laboratories. Celsius is for general use and set 0 and 100 as melting and boiling point of water respectively. To convert from C to K, add 273.15 to C.

Answer 2

Lord Kelvin defined the zero of his scale at the temperature where according to the classical theory of thermodynamics, all thermal motion ceases. This was equivalent to -273 deg C [later amended to -273.15 deg C].

The incremental unit was kept the same as the Celsius degree. This means that converting from Celsius to Kelvin requires adding 273[.15].