The Rankine scale (/ˈræŋkɪn/ RANG-kin) is an absolute scale of thermodynamic temperature named after the University of Glasgow engineer and physicist Macquorn Rankine, who proposed it in 1859.
[1] Similar to the Kelvin scale, which was first proposed in 1848,[1] zero on the Rankine scale is absolute zero, but a temperature difference of one Rankine degree (°R or °Ra) is defined as equal to one Fahrenheit degree, rather than the Celsius degree used on the Kelvin scale.
[2] The Rankine scale is used in engineering systems where heat computations are done using degrees Fahrenheit.
[3] The symbol for degrees Rankine is °R[2] (or °Ra if necessary to distinguish it from the Rømer and Réaumur scales).
By analogy with the SI unit kelvin, some authors term the unit Rankine, omitting the degree symbol.