# Rankine to Delisle (°R to °De) Source: https://www.unitconvertercalculator.com/temperature/rankine-to-delisle/ To convert Rankine to Delisle, use the formula: De = (671.67 - R) x 5/6. The Rankine scale is the absolute Fahrenheit scale used in US thermodynamic engineering, while the Delisle scale is the inverted 18th-century Russian scale. Water freezes at 491.67 degrees R (150 De) and boils at 671.67 degrees R (0 De). ## Formula °R via Kelvin to °De ## Conversion Table | Rankine (°R) | Delisle (°De) | |---|---| | 0 °R | 559.725 °De | | 100 °R | 476.39166666667 °De | | 200 °R | 393.05833333333 °De | | 300 °R | 309.72499999999 °De | | 400 °R | 226.39166666667 °De | | 459 °R | 177.225 °De | | 491.67 °R | 150 °De | | 500 °R | 143.05833333333 °De | | 530 °R | 118.05833333334 °De | | 559 °R | 93.89166666666 °De | | 600 °R | 59.725000000005 °De | | 671.67 °R | 0 °De | | 700 °R | -23.608333333335 °De | | 800 °R | -106.94166666666 °De | | 1000 °R | -273.60833333334 °De | ## Units ### Rankine (°R) An absolute temperature scale using Fahrenheit-sized degrees. 0 °R equals absolute zero. Used in some US engineering applications, especially thermodynamics. ### 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 Rankine scale was created by William Rankine, 1859, used in American aerospace and chemical engineering. 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 Rankine scale (used in American aerospace and chemical engineering) 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 Rankine to Delisle? Use the formula De = (671.67 - R) x 5/6. At the freezing point of water: 491.67 R = 150 De. At the boiling point: 671.67 R = 0 De. ### When would you need to convert Rankine 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 491.67 R = 150 De. Water boils at 671.67 R = 0 De. These two fixed points anchor both scales and provide easy verification of any conversion calculation. ## Non-Frequently Asked Questions ### Is Rankine the most American temperature scale nobody has heard of? Rankine is used daily by American chemical and aerospace engineers but is unknown to the general public. An American who has never taken a thermodynamics course has almost certainly never encountered Rankine. It is the insider's temperature scale - essential in certain engineering offices, invisible everywhere else. ### Why did anyone need an absolute Fahrenheit scale? In thermodynamics, temperature ratios matter. You cannot calculate heat engine efficiency using Fahrenheit because the zero point is arbitrary. Rankine solves this by starting at absolute zero while keeping Fahrenheit-sized degrees. American engineers who work with imperial units need Rankine the way international scientists need Kelvin. ### If Rankine degrees are the same size as Fahrenheit degrees, why not just use Fahrenheit? Because thermodynamic equations require absolute temperature. In Fahrenheit, 0 F is not the absence of heat - it is just a cold day. In Rankine, 0 R truly means zero thermal energy. 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