Rankine scale

The Rankine scale (/ˈræŋkɪn/) is an absolute scale of thermodynamic temperature named after the Glasgow University engineer and physicist Macquorn Rankine, who proposed it in 1859.[1]

Unit ofTemperature
Symbol°R, °Ra 
Named afterMacquorn Rankine


The Kelvin scale was first proposed in 1848.[1]

The Rankine scale is used in engineering systems where heat computations are done using degrees Fahrenheit.

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, the kelvin, some authors term the unit rankine, omitting the degree symbol.[3][4] 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
Absolute zero
(by definition)
0 K −273.15 °C −459.67 °F 0 °R
Freezing point of brine
(zero point of Fahrenheit scale, old definition)
255.37 K −17.78 °C 0 °F 459.67 °R
Freezing point of water[Note 1] 273.15 K 0 °C 32 °F 491.67 °R
Boiling point of water[Note 2] 373.1339 K 99.9839 °C 211.97102 °F 671.64102 °R

See alsoEdit


  1. ^ The ice point of purified water has been measured to be 0.000089(10) degrees Celsius – see Magnum 1995
  2. ^ For Vienna Standard Mean Ocean Water at one standard atmosphere (101.325 kPa) when calibrated solely per the two-point definition of thermodynamic temperature. Older definitions of the Celsius scale once defined the boiling point of water under one standard atmosphere as being precisely 100 °C. However, the current definition results in a boiling point that is actually 16.1 mK less. For more about the actual boiling point of water, see VSMOW in temperature measurement.


  1. ^ a b "Rankine". Merriam-Webster Dictionary. Retrieved 2019-11-07.
  2. ^ B.8 Factors for Units Listed Alphabetically from Thompson & Taylor 2008, pp. 45–69
  3. ^ Pauken 2011, p. 20
  4. ^ Balmer 2011, p. 10


External linksEdit