Formula – How to calculate Réaumur
| To Réaumur | From Réaumur | |
| Celsius (°C) | °C x (4/5) = °Ré | °Ré x (5/4) = °C |
| Fahrenheit (°F) | (°F – 32) x (4/9) = °Ré | °Ré x (9/4) + 32 = °F |
| Kelvin (K) | (K – 273.15) x (4/5) = °Ré | °Ré x (5/4) + 273.15 = K |
| Rankine (°R) | (°R – 491.67) x (4/9) = °Ré | °Ré x (9/4) + 491.67 = °R |
| Delisle (°De) | 80 – (°De x 8/5) = °Ré | (80 – °Ré) x 8/15 = °De |
| Rømer (°Rø) | (°Rø – 7.5) x (32/21) = °Ré | (°Ré x 21/32) + 7.5 = °Rø |
| Newton (°N) | °N x (80/33) = °Ré | °Ré x (33/80) = °N |
What is the Réaumur temperature scale?
Réaumur is a temperature first proposed in 1730.
It is defined as having the freezing point of water as 0° and the boiling point of water as 80°.
The scale was used some parts of Europe until the mid-19th century, and in parts of Russia until the early 20th century. It continues to have a use in cooking.
“Degrees of frost” is equivalent to the negative portion of the Réaumur scale. One degree of frost is one degree negative of Réaumur (11 degrees of frost, as quoted in the Brothers Karamazov would be -11°Ré).