The kelvin, symbol K, is the base unit of measurement for temperature in the International System of Units (SI). The Kelvin scale is an absolute temperature scale that starts from 0 K, the coldest possible temperature, then rises by exactly 1 K for each 1 °C. The Kelvin scale was designed to be easily converted from the Celsius scale. Any temperature in degrees Celsius can be converted to kelvin by adding 273.15.

Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making up a substance.