The Rankine scale is a temperature scale expressing absolute temperature in Fahrenheit degrees. It was devised by the Scottish engineer William Rankine (1820–1872). For Fahrenheit readings above zero, 460° is added. Thus, 72°F equals 460° plus 72°, or 532° absolute (532°R). If the Fahrenheit reading is below zero, it is subtracted from 460°. Thus, -40°F equals 460° minus 40°, or 420° absolute (420°R).