degree Réaumur
Temperatureexact by definition
The degree Réaumur puts 0 at the freezing point of water and 80 at the boiling point, so one Réaumur degree is exactly 1.25 K and T/K = (t/°Ré + 218.52) × 1.25. Both numbers are exact, since the scale is now defined off the Celsius scale it once competed with: t/°Ré = t/°C × 0.8.
Watch out: Older European sources abbreviate it °R, which is now Rankine in every engineering context. If a temperature written °R makes a person sound comfortable at 20, it is Réaumur; if water freezes at 491.67, it is Rankine. The scale survives today only in a few Italian and Swiss cheese and syrup recipes.
| 1 | 1.25 (offset scale) |
René Antoine Ferchault de Réaumur built the scale in 1730 around a dilute alcohol thermometer whose volume happened to grow by 80 parts in a thousand between the two fixed points, which is the whole reason for the odd 80. It was the standard scale in much of continental Europe for over a century and survived longest in Russia, where nineteenth-century Russian novels still quote it.
One degree réaumur in every temperature unit
| 274,400,000,000 | nanokelvin (nK) | |
| 274,400,000 | microkelvin (μK) | |
| 274,400 | millikelvin (mK) | |
| 34.25 | degree Fahrenheit (°F) | |
| 493.92 | degree Rankine (°R) | |
| 274.4 | kelvin (K) | |
| 1.25 | degree Celsius (°C) | |
| 1 | degree Réaumur (°Ré)this unit | |
| 0.2744 | kilokelvin (kK) | |
| 0.0002744 | megakelvin (MK) | |
| 2.74400e-07 | gigakelvin (GK) |