Reaumur to Celsius Converter
Enter the value that you want to convert Reaumur (°r) to Celsius (°C) or Celsius to Reaumur.Also written as °R to °C conversion.
1 Reaumur = 1.2500000 Celsius
Formula: °C = °Ré × 5/4
°R to °C — Reaumur to Celsius
10 Reaumur = 12.50000 Celsius
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How Reaumur Relates to Celsius
Understanding the Reaumur
The Réaumur scale sets water's freezing point at 0° and boiling point at 80°, created by French scientist René Antoine Ferchault de Réaumur in 1730.
Once widely used in Europe (particularly France, Germany, and Russia), the Réaumur scale (°Ré) has been almost entirely replaced by Celsius. However, it persists in some traditional industries: Italian and Swiss cheese-making (specifying milk temperatures during production), some French cooking traditions, and historical weather records. The scale is notable for having only 80 divisions between freezing and boiling, making each Réaumur degree 1.25 Celsius degrees.
Understanding the Celsius
The Celsius scale was proposed by Swedish astronomer Anders Celsius in 1742, originally with 0° as the boiling point and 100° as freezing — later inverted.
Celsius (°C) is the most widely used temperature scale globally, adopted by every country except the United States for everyday use. It sets water's freezing point at 0°C and boiling point at 100°C at standard atmospheric pressure. The scale is used in weather forecasts, cooking, medicine (normal body temperature ≈ 37°C), scientific research, and industrial processes worldwide. Since 1954, it has been defined relative to the Kelvin scale: °C = K − 273.15.
Temperature Scales in Context
Temperature conversion is one of the few non-linear unit conversions people encounter daily. Celsius dominates scientific work and most countries, Fahrenheit remains standard in the US for weather and cooking, Kelvin is required in thermodynamics and gas law calculations, and Rankine appears in some US engineering applications. Converting between these scales requires formulas rather than simple multiplication.
Reaumur to Celsius metric conversion table
| 0.01 °r | = | 0.01250 °C |
| 0.1 °r | = | 0.12500 °C |
| 1 °r | = | 1.25000 °C |
| 2 °r | = | 2.50000 °C |
| 3 °r | = | 3.75000 °C |
| 4 °r | = | 5.00000 °C |
| 5 °r | = | 6.25000 °C |
| 6 °r | = | 7.50000 °C |
| 7 °r | = | 8.75000 °C |
| 8 °r | = | 10.00000 °C |
| 9 °r | = | 11.25000 °C |
| 10 °r | = | 12.50000 °C |
| 11 °r | = | 13.75000 °C |
| 12 °r | = | 15.00000 °C |
| 13 °r | = | 16.25000 °C |
| 14 °r | = | 17.50000 °C |
| 15 °r | = | 18.75000 °C |
| 16 °r | = | 20.00000 °C |
| 17 °r | = | 21.25000 °C |
| 18 °r | = | 22.50000 °C |
| 19 °r | = | 23.75000 °C |
| 20 °r | = | 25.00000 °C |
| 30 °r | = | 37.50000 °C |
| 40 °r | = | 50.00000 °C |
| 50 °r | = | 62.50000 °C |
| 60 °r | = | 75.00000 °C |
| 70 °r | = | 87.50000 °C |
| 80 °r | = | 100.00000 °C |
| 90 °r | = | 112.50000 °C |
| 100 °r | = | 125.00000 °C |
| 200 °r | = | 250.00000 °C |
| 300 °r | = | 375.00000 °C |
| 400 °r | = | 500.00000 °C |
| 500 °r | = | 625.00000 °C |
| 600 °r | = | 750.00000 °C |
| 700 °r | = | 875.00000 °C |
| 800 °r | = | 1000.00000 °C |
| 900 °r | = | 1125.00000 °C |
| 1000 °r | = | 1250.00000 °C |
How to Convert °R to °C (Reaumur to Celsius)?
We can convert Reaumur to Celsius by using an example.
Example:
Convert 20 Reaumur to Celsius?
We know 1 Reaumur = 1.2500000 Celsius; 1 Celsius = 0.8000000 Reaumur.
20 Reaumur = ___°C
20 × 1.2500000 = 25.00000 °C (we know 1 Reaumur = 1.2500000 Celsius)
Answer:
20 Reaumur = 25.00000 Celsius
Réaumur to Celsius Conversion
Multiply by 5/4 (or 1.25) — the inverse of the 4/5 factor:
- Write down the Réaumur temperature.
- Multiply by 5/4 (or 1.25).
- The result is Celsius.
Solved Examples
Question 1: A historical recipe says "heat milk to 25°Ré." What is that in Celsius?
Solution:
°C = °Ré × 5/4
= 25 × 1.25
Answer: 25°Ré = 31.25°C
Question 2: Convert 80°Ré to Celsius.
Solution:
°C = 80 × 1.25
= 100
Answer: 80°Ré = 100°C (boiling point)
Question 3: Old German weather record shows -16°Ré. Celsius?
Solution:
°C = -16 × 1.25
= -20
Answer: -16°Ré = -20°C
Practice Questions
Try solving these on your own to test your understanding:
- Convert 40°Ré to Celsius. (Answer: 50°C)
- What is 60°Ré in Celsius? (Answer: 75°C)
- Convert -8°Ré to Celsius. (Answer: -10°C)
Reading Historical Temperature Records
European weather records from the 18th and 19th centuries often use Réaumur. Converting these to modern Celsius allows climate scientists to extend temperature datasets further back in time. French academy records, Russian imperial weather stations, and German scientific journals all used Réaumur extensively before the international adoption of Celsius in the mid-1800s.
Key Takeaways
- °C = °Ré × 5/4 (multiply by 1.25).
- 0°Ré = 0°C, 80°Ré = 100°C.
- Essential for interpreting pre-1850 European temperature records.
Reaumur to Celsius Conversion Formula
°C = °Ré × 5/4
1 Reaumur = 1.2500000 Celsius
1 Celsius = 0.8000000 Reaumur
Frequently Asked Questions
How many Celsius are in 1 Reaumur?
1 Reaumur equals 1.25000 Celsius. Note: Temperature conversion uses a formula, not simple multiplication.
How do I convert Reaumur to Celsius?
Use the conversion formula shown above. For example, 6.25 Celsius equals 5 Reaumur. Temperature scales have different zero points, so a formula (not simple multiplication) is required.
How do I convert Celsius to Reaumur?
Use the reverse formula. 1 Celsius equals 0.80000 Reaumur. See the formula section above for the exact equation.
What is 10 Reaumur in Celsius?
10 Reaumur is equal to 12.50000 Celsius.
What is 100 Reaumur in Celsius?
100 Reaumur is equal to 125.00000 Celsius.