19 December 2014
Julian Day:
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Online temperature conversion for: Amonton, Barnsdorf, Beaumuir, Bénart, Bergen, Brisson, Celsius, Cimento, Cruquius, Dalencé, Dalton, Daniell, De la Hire, De la Ville, Delisle [Newer], Delisle [Older], De Luc, De Lyon, de Revillas, Derham [I], Derham [II], de Suede, de Villeneuve, Du Crest, Edinburgh, electron volts, Fahrenheit, Fahrenheit [Pre-1707], Florentine [Large], Florentine [Small], Florentine Magnum, Fowler, Frick, Gas Mark, Goubert, Hales, Hanow [Newer], Hanow [Older], Hauksbee, Jacobs-Holborn, Kelvin, Kirch [Christine], Kirch [Gottfried], La Court, Lambert, Lange, Leiden, Ludolf, Mariotte, Miles, Murray, Newton, Oertel, Paris, Planck, Poleni, Réaumur, Rømer, Rankine, Richter, Rinaldini, Rosenthal, Royal Society of London, Sagredo, Saint-Patrice, Stufe, Sulzer, Thermostat, Wedgwood [Original], and Wedgwood [Modernized]

Temperature Unit Conversions

Behold the ultimate temperature conversion machine.

In early 2010 I stumbled across some charts from some eighteenth- and nineteenth-century sources on the subject of thermometers and was intrigued with the vast number of temperature scales that proliferated in those days. Most seem pretty obscure now, but many at one time or another, such as that of the Royal Society of London, enjoyed great popularity.

The systems of Anders Celsius (1701-1744); William Thomson, 1st Baron Kelvin (1824-1907); and Daniel Gabriel Fahrenheit (1686-1736) ultimately prevailed, of course, but you may have heard of a few others. The scale established by René Antoine Ferchault de Réaumur (1683-1757), in which freezing is zero and boiling is 80 degrees, still finds some use among European cheesemakers and often shows up in nineteenth-century literature such as Tolstoy’s War and Peace:

Christmas came and except for the ceremonial Mass, the solemn and wearisome Christmas congratulations from neighbors and servants, and the new dresses everyone put on, there were no special festivities, though the calm frost of minus twenty degrees Réaumur, the dazzling sunshine by day, and the starlight of the winter nights seemed to call for some special celebration of the season.

The Rankine scale is identical to the Fahrenheit, except that it avoids negative numbers by initializing at absolute zero (-459.67 °F). You encounter it from time to time in engineering literature. Its name honors William John Macquorn Rankine (1820-1872), who also left us the following comments regarding those newfangled metric units he strove to avoid:

Some talk of millimetres, and some of kilogrammes,
And some of decilitres, to measure beer and drams;
But I’m a British Workman, too old to go to school,
So by pounds I’ll eat, and by quarts I’ll drink,
And I’ll work by my three-foot rule.

John Dalton

With the exception of the Dalton scale all of these are linear. This means that given a known temperature scale reading of T1, the unknown value for another scale, T2, equals (m * T1) + b where m is called a slope and b a displacement. For Celsius to Fahrenheit, for example, Fahrenheit = (1.8*Celsius) + 32. As in the cases of older and newer Delisle, de Revillas, Hauksbee, and the Royal Society of London that slope can be negative. That indicates their numbers go down with increasing kinetic energy rather than up. The Celsius scale originally worked this way, with 100 freezing and 0 boiling, until it was flipped in the mid 1700s.

Daltons Kelvins Graph
John Dalton’s system is logarithmic. This is useful when you’re plotting temperatures that vary exponentially, such as among different star types. Absolute zero is negative infinity in this scale, freezing is 0.0 Daltons, water boils at 100, lead melts at around 253, and so forth. Every hundred Daltons multiplies the thermodynamic energy by the ratio 373.15/273.15 or approximately 1.37.

The converter below will translate between any pair of scales out of the 70. As a bonus it will display the formula for a direct conversion between them — that’s 4830 total sets — along with the values of any mathematical intersections. Since the Dalton scale is curved, it can share as many as two points with some linear ones.

From        To     

0 Celsius = 32 Fahrenheit
Formula: Fahrenheit = (1.8*Celsius) + 32

These two scales intersect mathematically at -40

Absolute zero0 K-273.15°C-459.67°F
Niobium superconducts9.26 K-263.89°C-443.00°F
Argon fluorohydride decomposes17.15 K-256.00°C-428.80°F
Lunar surface nighttime40 K-233.15°C-387.67°F
Pluto’s surface (mean)44 K-229.15°C-380.47°F
Nitrogen liquifies77.36 K-195.79°C-320.42°F
Titan’s surface (mean)94 K-179.15°C-290.47°F
Xenon freezes161.3 K-111.85°C-169.33°F
Satellite-measured earth lows179.817 K-93.33°C-136.00°F
Carbon dioxide freezes (“dry ice”)194.65 K-78.50°C-109.30°F
Fahrenheit & Celsius intersect233.15 K-40.00°C-40.00°F
Mercury freezes234.32 K-38.83°C-37.89°F
Brown dwarf star WISE 0855-0714238 K-35.15°C-31.27°F
Ice and salt water bath252.05 K-21.10°C-5.98°F
Triethylborane (TEB) auto-ignites253.65 K-19.50°C-3.10°F
Bromine freezes265.8 K-7.35°C18.77°F
Hibernating arctic ground squirrel270.25 K-2.90°C26.78°F
Water freezes273.15 K0.00°C32.00°F
Heavy water freezes276.97 K3.82°C38.88°F
Superheavy water freezes277.64 K4.49°C40.08°F
Lager fermentation (typical)278 K4.85°C40.73°F
Wine storage (ideal)285.9 K12.75°C54.95°F
Earth’s surface (mean)287.75 K14.60°C58.28°F
Ale fermentation (typical)294 K20.85°C69.53°F
Room temperature (typical)295.5 K22.35°C72.23°F
Brown dwarf WISE 1828+2650300 K26.85°C80.33°F
Gallium melts302.91 K29.76°C85.57°F
Giant anteater body temp.305.85 K32.70°C90.86°F
Butter melts (typical)306.65 K33.50°C92.30°F
White phosphorus auto-ignites307 K33.85°C92.93°F
White chocolate melts (typical)313.15 K40.00°C104.0°F
Milk chocolate melts (typical)315.65 K42.50°C108.5°F
Dark chocolate melts (typical)320.15 K47.00°C116.6°F
Xenon hexafluoride melts322.4 K49.25°C120.7°F
Hottest recorded Earth temp.330.95 K57.80°C136.0°F
Water boils373.15 K100.0°C212.0°F
Heavy water boils374.6 K101.4°C214.5°F
Superheavy water boils374.7 K101.5°C214.7°F
Flaxseed oil smoke point380.2 K107.0°C224.6°F
Sulphur melts388.4 K115.2°C239.4°F
Lunar surface daytime396.0 K122.9°C253.1°F
Sugar carmelizes (typical)441.5 K168.4°C335.0°F
Kola Superdeep Borehole (12,262 m)453.2 K180.0°C356.0°F
Paper auto-ignites (typical)505.0 K231.9°C449.3°F
Mustard oil smoke point527.2 K254.0°C489.2°F
Amber melts573.0 K299.9°C571.7°F
Lead melts600.6 K327.5°C621.4°F
Mercury boils629.9 K356.7°C674.1°F
Zinc melts692.9 K419.7°C787.5°F
Venus’s surface (mean)735.0 K461.9°C863.3°F
Self-cleaning oven cycle (typical)775.0 K501.9°C935.3°F
Buckminsterfullerene (C60) sublimes873.2 K600.0°C1,112°F
Magnesium ribbon auto-ignites903.0 K629.9°C1,166°F
Cigarette tip during draw973.2 K700.0°C1,292°F
Table salt melts1,074 K800.9°C1,474°F
Gold melts1,337 K1,064°C1,948°F
Hard-paste porcelain firing1,673 K1,400°C2,552°F
Table salt boils1,686 K1,413°C2,575°F
Iron melts1,811 K1,538°C2,800°F
Lead boils2,022 K1,749°C3,180°F
Light bulb filament (typical)2,820 K2,547°C4,616°F
Gold boils3,129 K2,856°C5,173°F
Iron boils3,134 K2,861°C5,182°F
Oxyacetylene flame3,350 K3,077°C5,570°F
Diamond melts3,550 K3,277°C5,930°F
Tungsten melts3,695 K3,422°C6,191°F
Tantalum Hafnium Carbide melts4,488 K4,215°C7,619°F
Diamond boils5,100 K4,827°C8,720°F
Dicyanoacetylene flame5,260 K4,987°C9,008°F
Solar surface5,799 K5,526°C9,979°F
Tungsten boils5,828 K5,555°C10,031°F
Earth’s center (inferred)6,230 K5,957°C10,754°F

Please note that the conversions between temperatures on this page are not guaranteed. The definitions of some of these scales, especially the more obscure ones, fall far short of modern standards for precision and reproducibility — so any results among them beyond two or three digits to the right of the decimal point should be taken with a colossal grain of salt.

The units Gas Mark, Stufe, and Thermostat appear on some kitchen ovens (in England, Austria, and France respectively) and their data comes from Martha Stewart. Special thanks also to Benny Freilow, Beate and Rainer Holland, and Enrico Schulze for their advice and enhancements. If you spot any errors that you can correct, or know of any other scales I might be able to include, please feel free to contact me.

Arctic Ground Squirrel Arctic

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