How this calculator works
Each scale is an affine transformation of modern Celsius, with a fixed size of degree and zero point. Kelvin shares the Celsius interval but starts at absolute zero. Rankine shares the Fahrenheit interval. The historical scales are shown using their conventional modern linear equivalents, not as a calibration of an original instrument. Delisle runs in the opposite direction, so a hotter temperature has a smaller Delisle reading.
Formula
F = 9C/5 + 32; K = C + 273.15; Rankine = 9C/5 + 491.67; Delisle = 150 - 3C/2; Newton = 33C/100; Réaumur = 4C/5; Rømer = 21C/40 + 7.5. Reverse a scale with C = (reading - offset) / slope.
Worked example
At 20 °C, the readings are 68 °F, 293.15 K, 527.67 °R, 120 °De, 6.6 °N, 16 °Ré and 18 °Rø. A reverse reading of 80 °Ré gives 100 °C.
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Frequently asked questions
How is this different from a Celsius to Fahrenheit tool?
It includes five less common historical scales and reverse conversion from each, with a common-temperature table for the selected scale.
Can I convert a temperature difference with these formulas?
For an interval, apply only the slope and omit the offset. This tool expects an actual temperature, so it includes each scale zero point.
Why can Delisle readings decrease as Celsius rises?
The conventional Delisle scale assigns 150 to the freezing reference and zero to the boiling reference. Its degree direction is reversed.