Convert from degree Reaumur to degree Celsius

Unit Definition (degree Reaumur)
The degree Réaumur is a unit of temperature formerly used in continental Europe. The Réaumur temperature scale is named for the French scientist René-Antoine Ferchault de Réaumur (1683-1757). It is similar to the Celsius scale in having its zero point at the freezing temperature of water, but the interval between the freezing and boiling temperatures of water equals 80 °r instead of 100 °C. Therefore, 1 °r equals 1.25 °C or 2.25 °F.

Unit Definition (degree Celsius)
Degree Celsius is the most common metric unit of temperature. It was named after the Swedish astronomer and physicist Anders Celsius. The freezing point of water (at 1atm.) was originally defined to be 0°C and the boiling point at 100°C. It should be noted that the scale of the two units, degrees Celsius and degrees Kelvin are actually the same, although degrees Celsius is actually offset by 273° when compared to the Kelvin scale. 0° Kelvin (-273°C) is defined at the point at which all molecular motion stops.