Rankine scale

Rankine is a thermodynamic (absolute) temperature scale named after the Scottish engineer and physicist William John Macquorn Rankine, who proposed it in 1859.

The symbol is R (or Ra if necessary to distinguish it from the Rømer and Réaumur scales). As with the Kelvin scale (symbol: K), zero on the Rankine scale is absolute zero, but the Rankine degree is defined as equal to one degree Fahrenheit, rather than the one degree Celsius used by the Kelvin scale. A temperature of -459.67 °F is exactly equal to 0 R.

A few engineering fields in the U.S. measure thermodynamic temperature using the Rankine scale. However, throughout the scientific world where measurements are made in SI units, thermodynamic temperature is measured in kelvin.

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