# Rømer to Delisle (°Rø to °De) Source: https://www.unitconvertercalculator.com/temperature/romer-to-delisle/ To convert Romer to Delisle, use the formula: De = (60 - Ro) x 20/7. The Romer scale is the early Danish scale that influenced Fahrenheit, while the Delisle scale is the inverted 18th-century Russian scale. Water freezes at 7.5 degrees Ro (150 De) and boils at 60 degrees Ro (0 De). ## Formula °Rø via Kelvin to °De ## Conversion Table | Rømer (°Rø) | Delisle (°De) | |---|---| | -10 °Rø | 199.99999999999 °De | | 0 °Rø | 171.42857142856 °De | | 5 °Rø | 157.14285714285 °De | | 7.5 °Rø | 150 °De | | 10 °Rø | 142.85714285715 °De | | 15 °Rø | 128.57142857143 °De | | 20 °Rø | 114.28571428572 °De | | 25 °Rø | 100 °De | | 30 °Rø | 85.71428571429 °De | | 40 °Rø | 57.14285714286 °De | | 50 °Rø | 28.57142857143 °De | | 60 °Rø | 0 °De | | 80 °Rø | -57.14285714286 °De | | 100 °Rø | -114.28571428572 °De | | 200 °Rø | -400.00000000001 °De | ## Units ### Rømer (°Rø) A temperature scale proposed by Ole Christensen Rømer in 1701. Water freezes at 7.5 °Rø and boils at 60 °Rø. It influenced Fahrenheit's scale development. ### 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 Romer scale was created by Ole Romer, Danish astronomer, around 1701, influenced Fahrenheit. 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 Romer scale (influenced Fahrenheit) 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 Romer to Delisle? Use the formula De = (60 - Ro) x 20/7. At the freezing point of water: 7.5 Ro = 150 De. At the boiling point: 60 Ro = 0 De. ### When would you need to convert Romer 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 7.5 Ro = 150 De. Water boils at 60 Ro = 0 De. These two fixed points anchor both scales and provide easy verification of any conversion calculation. ## Non-Frequently Asked Questions ### Is the Romer scale Fahrenheit's secret parent? In a sense, yes. Fahrenheit visited Ole Romer in 1708 and studied his thermometric methods. Fahrenheit then modified Romer's approach, expanding the scale and changing the reference points. Without Romer, Fahrenheit might never have developed his scale. The Romer scale is the ancestor that America's temperature system has largely forgotten. ### Why does water freeze at 7.5 degrees Romer? Romer set 0 degrees at the freezing point of brine (salt water), not pure water. Pure water happened to freeze at 7.5 on his scale. This seemingly random number is actually a physical measurement result, not a design choice. Fahrenheit adopted the same brine-zero concept, which is why water freezes at the equally arbitrary 32 F. ### Is the Romer scale used for anything today? Not in any active measurement context. It survives solely in conversion tables, history-of-science texts, and the occasional pub quiz question. Its most lasting contribution was inspiring Fahrenheit, whose scale then became the standard for 300 million Americans. 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