Réaumur to Celsius Converter

The Réaumur scale sets the freezing point of water at 0 degrees and the boiling point at 80 degrees, so it divides that range into 80 units instead of Celsius's 100. It was widely used in Europe in the 18th and 19th centuries and still appears in some cheese and syrup making.

Multiply the Réaumur value by 1.25 (that is, 5/4): °C = °Ré x 1.25. For example, 80 °Ré equals 100 °C. To go back, multiply Celsius by 0.8: °Ré = °C x 4/5.

Both scales span the same physical range from water's freezing to boiling point, but Réaumur splits it into 80 parts and Celsius into 100. So each Réaumur degree covers 100/80 = 1.25 Celsius degrees.

Rarely, and mostly by tradition. Some Italian and Swiss cheese recipes and a few older European references still quote Réaumur temperatures, but science and industry use Celsius or Kelvin. This converter is handy for reading old recipes and texts.