# Kelvin to Réaumur (K to °Ré) Source: https://www.unitconvertercalculator.com/temperature/kelvin-to-reaumur/ To convert Kelvin to Reaumur, use the formula: Re = (K - 273.15) x 4/5. The Kelvin scale is the absolute SI temperature unit used in science worldwide, while the Reaumur scale is the historical European scale once standard in France and Germany. Water freezes at 273.15 degrees K (0 Re) and boils at 373.15 degrees K (80 Re). ## Formula K via Kelvin to °Ré ## Conversion Table | Kelvin (K) | Réaumur (°Ré) | |---|---| | 0 K | -218.52 °Ré | | 4 K | -215.32 °Ré | | 20 K | -202.52 °Ré | | 77 K | -156.92 °Ré | | 100 K | -138.52 °Ré | | 173 K | -80.12 °Ré | | 200 K | -58.52 °Ré | | 233 K | -32.12 °Ré | | 253 K | -16.12 °Ré | | 273.15 K | 0 °Ré | | 293 K | 15.88 °Ré | | 298 K | 19.88 °Ré | | 300 K | 21.48 °Ré | | 310 K | 29.48 °Ré | | 373.15 K | 80 °Ré | | 400 K | 101.48 °Ré | | 500 K | 181.48 °Ré | | 1000 K | 581.48 °Ré | | 5000 K | 3781.48 °Ré | | 10000 K | 7781.48 °Ré | ## Units ### Kelvin (K) The SI base unit of temperature. 0 K is absolute zero, the theoretical lowest possible temperature. Used in science and engineering. ### Réaumur (°Ré) A historical temperature scale where water freezes at 0 °Ré and boils at 80 °Ré. Named after René Antoine Ferchault de Réaumur. Once widely used in Europe. ## Background The Kelvin scale was created by Lord Kelvin (William Thomson), 1848, the SI standard for thermodynamics. The Reaumur scale was created by Rene Antoine Ferchault de Reaumur, 1730, once widespread in continental Europe. Converting between them bridges different eras and different measurement philosophies in the history of thermometry. ## Good to Know The history of temperature measurement is the history of scientific collaboration and competition across borders. The Kelvin scale (the SI standard for thermodynamics) and the Reaumur scale (once widespread in continental Europe) represent different national contributions to solving the same fundamental problem: how to assign numbers to the sensation of hot and cold. ## FAQ ### How do you convert Kelvin to Reaumur? Use the formula Re = (K - 273.15) x 4/5. At the freezing point of water: 273.15 K = 0 Re. At the boiling point: 373.15 K = 80 Re. ### When would you need to convert Kelvin to Reaumur? This conversion is needed when interpreting historical scientific records, comparing temperature data across different measurement traditions, or completing engineering calculations that mix temperature scales from different national standards. ### What are the key reference points for both scales? Water freezes at 273.15 K = 0 Re. Water boils at 373.15 K = 80 Re. These two fixed points anchor both scales and provide easy verification of any conversion calculation. ## Non-Frequently Asked Questions ### Would a physicist find Reaumur charming or frustrating? Charming historically, frustrating practically. Reaumur's 0-to-80 range for liquid water is elegant in its own way, but every thermodynamic equation would need modified constants. Kelvin aligns with the fundamental physics of energy and entropy. Reaumur aligns with the practical experience of boiling water. Physics chose Kelvin; cooking chose neither. ### At what Reaumur temperature does helium liquefy? Helium liquefies at about 4.2 Kelvin, which is approximately -215.16 degrees Reaumur. This deeply negative Reaumur number shows why the scale was never adopted for cryogenic science. Reaumur works well for the kitchen range of 0 to 80 but produces absurd numbers at the extremes that modern science routinely explores. ### Is Kelvin-to-Reaumur the most mismatched temperature conversion? It bridges an absolute thermodynamic scale (Kelvin) with a domestic empirical scale (Reaumur). One was designed for calculating the entropy of black holes; the other for checking if your soup is warm enough. The mismatch is not mathematical - the conversion works perfectly - but philosophical. 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