# Réaumur to Delisle (°Ré to °De) Source: https://www.unitconvertercalculator.com/temperature/reaumur-to-delisle/ To convert Reaumur to Delisle, use the formula: De = (80 - Re) x 15/8. The Reaumur scale is the historical European scale once standard in France and Germany, while the Delisle scale is the inverted 18th-century Russian scale. Water freezes at 0 degrees Re (150 De) and boils at 80 degrees Re (0 De). ## Formula °Ré via Kelvin to °De ## Conversion Table | Réaumur (°Ré) | Delisle (°De) | |---|---| | -30 °Ré | 206.25 °De | | -20 °Ré | 187.5 °De | | -10 °Ré | 168.75 °De | | 0 °Ré | 150 °De | | 5 °Ré | 140.625 °De | | 10 °Ré | 131.25 °De | | 15 °Ré | 121.875 °De | | 20 °Ré | 112.5 °De | | 25 °Ré | 103.125 °De | | 30 °Ré | 93.75 °De | | 40 °Ré | 75 °De | | 50 °Ré | 56.25 °De | | 60 °Ré | 37.5 °De | | 70 °Ré | 18.75 °De | | 80 °Ré | 0 °De | | 100 °Ré | -37.5 °De | | 200 °Ré | -225 °De | ## Units ### 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. ### Delisle (°De) A historical inverted temperature scale invented by Joseph-Nicolas Delisle in 1732. Water boils at 0 °De and freezes at 150 °De. Higher numbers mean colder temperatures. ## Background The Reaumur scale was created by Rene Antoine Ferchault de Reaumur, 1730, once widespread in continental Europe. The Delisle scale was created by Joseph-Nicolas Delisle, French astronomer, 1732, used in Russia. 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 Reaumur scale (once widespread in continental Europe) and the Delisle scale (used in Russia) 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 Reaumur to Delisle? Use the formula De = (80 - Re) x 15/8. At the freezing point of water: 0 Re = 150 De. At the boiling point: 80 Re = 0 De. ### When would you need to convert Reaumur to Delisle? 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 0 Re = 150 De. Water boils at 80 Re = 0 De. These two fixed points anchor both scales and provide easy verification of any conversion calculation. ## Non-Frequently Asked Questions ### Is Reaumur the temperature scale that cheese remembers? In some European cheese-making traditions, Reaumur degrees still appear in old recipes and guild documentation. A traditional instruction like 'heat the milk to 30 degrees Reaumur' (37.5 C) preserves an 18th-century measurement practice. The cheese does not care which scale is used, but the tradition maintains Reaumur as a culinary ghost. ### Why did Reaumur set boiling at 80 instead of 100? Reaumur calibrated his thermometer using diluted alcohol, where 80 divisions of expansion corresponded to the range from freezing to boiling water. The number 80 was a physical result of his alcohol-based instrument, not a deliberate design choice. Celsius later chose 100 divisions for the same range, producing the cleaner 0-100 scale that eventually won global adoption. ### Could Reaumur survive as a retro temperature scale? In the way that vinyl records survived alongside digital music, Reaumur could theoretically persist as a nostalgic reference. Some German and French culinary texts still mention Reaumur, and vintage thermometers marked in Reaumur appear in antique shops. 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