Celsius to Romer
°C
°Rø
Conversion History
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|---|---|---|
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Quick Reference Table (Celsius to Romer)
| Celsius (°C) | Romer (°Rø) |
|---|---|
| -40 | -13.5 |
| 0 | 7.5 |
| 20 | 18 |
| 37 | 26.925 |
| 100 | 60 |
About Celsius (°C)
Celsius (°C) is the most widely used temperature scale in the world, adopted by every country except the United States, Liberia, and Myanmar for everyday and scientific use. Zero degrees Celsius is defined as the freezing point of water at standard atmospheric pressure; 100°C is the boiling point. Originally called centigrade because of its 100-degree span between these two reference points, it was renamed Celsius in 1948 to honor Swedish astronomer Anders Celsius. It is the practical temperature scale for weather, cooking, medicine, and most scientific work outside thermodynamics. Body temperature is 37°C; a comfortable room is typically 20–22°C.
Water freezes at 0°C and boils at 100°C. Normal human body temperature is 37°C. A warm summer day in southern Europe is around 35°C.
Etymology: Named after Swedish astronomer Anders Celsius (1701–1744), who proposed a 100-degree scale in 1742. His original scale was inverted — 0°C meant boiling, 100°C meant freezing — and was reversed by fellow Swede Carl Linnaeus shortly after his death.
About Romer (°Rø)
The Rømer scale (°Rø) is a historical temperature scale created by Danish astronomer Ole Christensen Rømer in 1701 — one of the earliest quantitative thermometric scales. Rømer set 7.5°Rø as the freezing point of water and 60°Rø as the boiling point. The lower reference of 0°Rø was set below the coldest Danish winter temperature to avoid negative readings. Body temperature is approximately 22.5°Rø. The Rømer scale is historically significant because Daniel Gabriel Fahrenheit visited Rømer in Copenhagen in 1708, was directly inspired by his work, and later developed the Fahrenheit scale partly building on Rømer's two-point calibration method. Today it is purely of historical interest.
The freezing point of water is 7.5°Rø. A pleasant summer day (25°C) is approximately 20.6°Rø. Boiling water is 60°Rø.
Etymology: Named after Ole Christensen Rømer (1644–1710), the Danish astronomer who also made the first quantitative measurement of the speed of light in 1676, using observations of Jupiter's moon Io. He proposed the temperature scale around 1701 using wine and water thermometers with two fixed calibration points.
Celsius – Frequently Asked Questions
Which countries use Celsius?
Almost every country in the world uses Celsius for everyday temperatures — weather forecasts, cooking, and body temperature. The United States, Liberia, and Myanmar are the principal exceptions, using Fahrenheit for daily life, though US scientists use Celsius for research.
What is absolute zero in Celsius?
Absolute zero — the theoretical minimum temperature where molecular motion effectively ceases — is −273.15°C. This corresponds to 0 K on the kelvin scale. It is not physically achievable but has been approached to within a few billionths of a degree in laboratory conditions.
How do you convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 (or 1.8) and add 32. For example, 20°C × 1.8 + 32 = 68°F. A quick mental approximation: double the Celsius value and add 30 (gives ±2°F accuracy for typical weather temperatures).
What is normal body temperature in Celsius?
Normal human body temperature is approximately 37.0°C (98.6°F), though it varies by individual, time of day, and measurement site. A temperature above 38.0°C is generally considered a fever; hypothermia is diagnosed below 35.0°C.
What is the difference between Celsius and centigrade?
Centigrade is the old name for the same scale — both refer to a 100-degree span between water's freezing and boiling points ("centi" = 100, "grade" = step). The name was officially changed to Celsius in 1948 to avoid confusion with the angular unit also called "grade" (or "gradian") in some languages.
Romer – Frequently Asked Questions
Who invented the Rømer scale?
The Rømer scale was created by Danish astronomer Ole Christensen Rømer around 1701. Rømer is also famous for being the first person to measure the speed of light quantitatively in 1676, determining it by observing time variations in the eclipses of Jupiter's moon Io from different positions of Earth in its orbit.
Why is the freezing point of water 7.5°Rø and not 0°Rø?
Rømer set 0°Rø below the coldest temperature he expected in Denmark so that all practical outdoor measurements would be positive. This was a common design principle for early thermometric scales — avoiding negative values in everyday use. The 7.5 value arose from his calibration methodology using two fixed reference points and dividing the interval into 52.5 equal parts.
What is body temperature on the Rømer scale?
Normal body temperature (37°C) is approximately 22.5°Rø on the Rømer scale. Rømer himself used body temperature as one of his calibration reference points, which Fahrenheit later borrowed when constructing the Fahrenheit scale — translating Rømer's body temperature reference into his own 96°F calibration point.
How did Rømer influence Fahrenheit?
Daniel Gabriel Fahrenheit visited Ole Rømer in Copenhagen in 1708 and observed his thermometers and calibration method. Fahrenheit adopted Rømer's idea of using two fixed reference points and the principle of avoiding negative temperatures in common conditions. He then redesigned the scale — multiplying Rømer's degrees by approximately 4 and shifting the zero — to achieve finer graduation and a different zero point.
Could the Rømer scale have become the world standard instead of Celsius?
Unlikely. Rømer's scale had an awkward 7.5°Rø freezing point and a 52.5-degree span — not easy to memorize or subdivide cleanly. Celsius's 0-to-100 design was simpler, aligned with the decimal metric system sweeping Europe, and gained powerful institutional backing from Swedish and French academies. Fahrenheit's scale — partly derived from Rømer's — won in the English-speaking world largely due to British imperial reach. Rømer's real legacy is indirect: inspiring Fahrenheit, who then dominated for 250 years.