Kelvin - The Kelvin scale is an absolute, thermodynamic temperature scale with a null point of absolute zero. This is the point at which all thermal motion ceases. Kelvin measurements are denoted by the letter K and incremented in degrees like Fahrenheit and Celsius. In order to convert a measurement in Celsius to a measurement in Kelvin, 273.15 must be added to the Celsius measurement. The reverse must be done to convert Kelvin to Celsius. Kelvin is not referred to or typeset as a degree. The Kelvin temperature scale is the primary unit of measurement in the physical sciences.