# Rankine scale

The Rankine scale (/ˈræŋkɪn/) is an absolute scale of thermodynamic temperature named after the Glasgow University engineer and physicist William John Macquorn Rankine, who proposed it in 1859. (The Kelvin scale was first proposed in 1848.) It may be used in engineering systems where heat computations are done using degrees Fahrenheit.

Rankine
Unit ofTemperature
Symbol°R, °Ra
Named afterWilliam John Macquorn Rankine

The symbol for degrees Rankine is °R (or °Ra if necessary to distinguish it from the Rømer and Réaumur scales). By analogy with Kelvin, some authors term the unit Rankine, omitting the degree symbol. Zero on both the Kelvin and Rankine scales is absolute zero, but a temperature difference of one Rankine degree is defined as equal to one Fahrenheit degree, rather than the Celsius degree used on the Kelvin scale. Thus, a temperature of 0 K (−273.15 °C; −459.67 °F) is equal to 0 °R, and a temperature of −458.67 °F equal to 1 °R.

Some important temperatures relating the Rankine scale to other temperature scales are shown in the table below.

Kelvin Celsius Fahrenheit Rankine 0 K −273.15 °C −459.67 °F 0 °R 255.37 K −17.78 °C 0 °F 459.67 °R 273.15 K 0 °C 32 °F 491.67 °R 373.1339 K 99.9839 °C 211.97102 °F 671.64102 °R