Convert grad Rømer to Rankine

The kelvin is written without a degree sign and starts at absolute zero: 0 K = −273.15 °C, and a difference of 1 K is the same as a difference of 1 °C. Fahrenheit sets the freezing and boiling points of water at 32 °F and 212 °F, so °F = °C × 9/5 + 32; the two scales meet at −40°. Body temperature is 37 °C = 98.6 °F, a hot summer day 30 °C = 86 °F. The Rankine scale is to Fahrenheit what the kelvin is to Celsius, an absolute scale in Fahrenheit-sized steps, used in some US engineering.

Before Celsius won out, each country had its own thermometer. Réaumur (1730) put water's freezing point at 0 °Ré and its boiling point at 80 °Ré; the scale was standard in France, Germany and Russia through the 19th century and survives in a few Alpine cheese dairies. Delisle (1732) ran backwards, 0 at boiling and 150 at freezing, and was used in Russia for about a century. Rømer's scale (1701) has freezing at 7.5° and boiling at 60°, and Newton's (1701) freezing at 0 and boiling at 33.