Kelvin

The kelvin scale starts at absolute zero (0 K = $-273$ $^\circ$C). The size of one kelvin is the same as one degree Celsius.

$T(\text{K}) = \theta(^\circ\text{C}) + 273$

The kelvin is written without a degree symbol. Gas law calculations require temperatures in kelvin because the Celsius scale’s zero does not correspond to zero particle energy.