Degree Rømer (°Rø)

ScandinavianHistorical unit (no longer in standard use)

An early temperature scale devised by Ole Rømer around 1702: water freezes at 7.5° and boils at 60°. Fahrenheit based his scale on it.

0 degrees Rømer = 258.8642857 kelvins (approximately).

About the degree Rømer

Ole Rømer, the Danish astronomer better known for measuring the speed of light, devised this scale around 1702 for his own use. It is the second temperature scale on record, after Newton's from a year earlier. Water freezes at 7.5 degrees and boils at 60 degrees, so one degree equals 40/21 of a Celsius degree, about 1.905 degrees Celsius.

The odd 7.5 may come from his earlier choice of a lower fixed point, the cold of ammonium chloride brine. He apparently found that the freezing point of water lay about one eighth of the way up from that mark to boiling and moved the scale accordingly, though his exact reasoning is unknown.

Daniel Fahrenheit visited him in Copenhagen in 1708 and by 1713 was making thermometers on a scale largely borrowed from Rømer. He shifted freezing from 7.5 to 8 and quartered each degree, which gave 32 degrees. Rømer's notebook was only published in 1910.

Sources: Wikipedia: Rømer scale; Wikipedia: Ole Rømer

Degree Rømer conversion chart

100 degrees Rømer expressed in every other temperature unit:

More Scandinavian units

• Scandinavian mil (length)
• streck (Swedish mil) (angle)
• liter per mil (fuel economy)

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