Convert Romer to Reaumur temperature scales effortlessly
(1 °Rø - 7.5) x 32÷21 = -9.905 °Re
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Imagine finding an 18th-century Danish cookbook with temperature notes in Rømer, or French scientific notes using Réaumur. These pre-Celsius scales tell stories of early temperature measurement. Our converter bridges these historical systems, preserving accuracy while satisfying modern curiosity. Let's explore why these scales mattered and how they connect.
Unit definitions
What is a Rømer (°Rø)?
Copenhagen astronomer Ole Christensen Rømer created this scale in 1701. It used brine's freezing point (7.5°Rø) and water boiling (60°Rø) as fixed points. The scale became Denmark's official temperature standard until 1860. Fun fact: Fahrenheit visited Rømer and based his own scale on these concepts.
Symbol: °Rø
Common uses: Historical Danish records, early thermodynamics experiments
Definition: 0°Rø = freezing point of brine, 60°Rø = boiling water
What is a Réaumur (°Re)?
French scientist René Antoine Ferchault de Réaumur proposed this in 1730. It sets water's freezing point at 0°Re and boiling at 80°Re. The 80-degree range made calculations simpler in pre-decimal Europe. Surprisingly, some Russian factories used it until the 1917 revolution.
Symbol: °Re
Common uses: 18th-century European science, vintage wine-making guides
Definition: 0°Re = water freezing, 80°Re = water boiling
Conversion formula
The mathematical relationship is:
Réaumur = (Rømer - 7.5) × 32/21
Rømer = (Réaumur × 21/32) + 7.5
Example calculations
- Converting 30°Rø to Réaumur:
(30 - 7.5) = 22.5
22.5 × 32 = 720
720 ÷ 21 ≈ 34.29°Re - Converting 15°Re to Rømer:
15 × 21 = 315
315 ÷ 32 ≈ 9.84
9.84 + 7.5 = 17.34°Rø
Conversion tables
Rømer to Réaumur
| Rømer (°Rø) | Réaumur (°Re) |
|---|---|
| 0 | -11.43 |
| 7.5 | 0.00 |
| 15 | 11.43 |
| 30 | 34.29 |
| 40 | 47.62 |
| 50 | 60.95 |
| 60 | 74.29 |
Réaumur to Rømer
| Réaumur (°Re) | Rømer (°Rø) |
|---|---|
| -20 | -5.63 |
| 0 | 7.50 |
| 20 | 20.63 |
| 40 | 33.75 |
| 60 | 46.88 |
| 80 | 60.00 |
Historical context of temperature scales
The early 18th century was a golden age of temperature measurement. Scientists competed to create reliable scales, often basing them on strange references (Rømer initially used a mixture of ice and ammonium chloride). Réaumur's choice of 80 degrees between freezing and boiling made division easier in an era of fractions. Both scales eventually lost ground to Celsius' decimal-friendly system, but their legacy remains in historical archives.
An interesting sidenote: Russia's adoption of Réaumur created confusion. When Celsius scales arrived, some records listed temperatures in "grad Réaumur" alongside metric units. This dual system persisted in Siberia until the 1920s, benefit of standardized education.
Interesting facts
- Rømer's original thermometer used red wine instead of mercury
- The Réaumur scale was accidentally recreated in 2013 by a Swiss watchmaker
- 1°Re equals 1.25°C exactly
- Fahrenheit improved Rømer's scale by multiplying intervals by 4
- Some Spanish monasteries still use Réaumur for chocolate tempering
FAQ
These scales are mostly historical curiosities, but useful for interpreting old scientific texts or European recipes from the 18th century.
France, Germany and Russia used it until the 19th century. Some Alpine cheesemakers still reference it unofficially.
The formulas are mathematically exact, but original measurements from the 1700s might have had instrumental errors.
While possible, we recommend using Celsius or Fahrenheit for better compatibility with modern kitchen tools.
Carl Linnaeus used Réaumur's scale in early botanical studies. Rømer's work directly influenced Fahrenheit's improvements.