Convert Rømer to Celsius easily.

Ever wondered how scientists in the 17th century measured temperature? Before Celsius and Fahrenheit became household names, Ole Christensen Rømer’s scale was the talk of Europe. Today, converting Rømer to Celsius feels like decoding a piece of scientific history. Whether you’re restoring an antique thermometer or just satisfying a curiosity, our tool and guide make it straightforward.

Unit definitions

What is a Rømer (°Rø)?

Description: The Rømer scale, invented by Danish astronomer Ole Christensen Rømer in 1701, was one of the earliest standardized temperature systems.
Symbol: °Rø
Common uses: Historical scientific measurements, particularly in Scandinavia.
Definition: The scale sets water’s freezing point at 7.5°Rø and boiling point at 60°Rø, creating 52.5 divisions between these markers.

What is a Celsius (°C)?

Description: The Celsius scale, developed by Swedish astronomer Anders Celsius in 1742, is the global standard for temperature measurement outside the United States.
Symbol: °C
Common uses: Weather reports, cooking, scientific research.
Definition: Water freezes at 0°C and boils at 100°C under standard atmospheric pressure, divided into 100 equal intervals.

Conversion formula

To convert Rømer to Celsius:
°C = (°Rø - 7.5) × 40/21

This formula adjusts for the offset (7.5) and scales the interval size difference between the two systems.

Example calculations

1. Converting 30°Rø to Celsius:
   (30 - 7.5) = 22.5
   22.5 × 40/21 ≈ 42.86°C
2. Converting 0°C to Rømer:
   (0 × 21/40) + 7.5 = 7.5°Rø

Conversion tables

Rømer to Celsius

Celsius to Rømer

Historical background

The Rømer scale emerged from a need for reproducible temperature measurements. Ole Rømer, better known for calculating the speed of light, designed his scale around two fixed points: freezing brine (0°Rø) and boiling water (60°Rø). His work directly influenced Daniel Fahrenheit, who visited Rømer’s lab and later adjusted his scale to avoid fractions, creating the Fahrenheit system we know today.

Anders Celsius proposed his scale in 1742, initially inverting the modern values (0°C for boiling, 100°C for freezing). After his death, colleagues flipped the scale to its current form, simplifying it for broader adoption. The Celsius scale’s benifit lay in its decimal structure, aligning perfectly with the metric system’s rise in the 19th century.

Interesting facts

1. Astronomy meets thermometry: Rømer’s temperature work was a side project to his main research on planetary motions.
2. A thermometer in the pub: Early Rømer thermometers were sometimes found in Danish breweries to monitor fermentation.
3. Celsius’s original inversion: His “reversed” scale confused many until the posthumous flip resolved the issue.
4. Rømer’s legacy: Fahrenheit’s scale retains Rømer’s 7.5° offset, visible when comparing freezing points.
5. A universal language: Celsius became the global standard partly due to its role in the 1960 International System of Units (SI).

FAQ