Convert Reaumur to Celsius - Temperature Converter
This tool converts temperatures from the Réaumur scale (°Ré) to the Celsius scale (°C) using the exact linear relationship between the two scales. It is intended for quick conversions, documentation, and educational use.
The conversion implemented here is a pure mathematical transformation and does not account for measurement uncertainty from instruments or environmental factors. For metrology, calibration, or regulated reporting, follow recognized standards and laboratory procedures cited below.
Interactive Converter
Convert between reaumur and celsius with precision rounding.
Quick reference table
| Reaumur | Celsius |
|---|---|
| 1 °Ré | 1.25 °C |
| 5 °Ré | 6.25 °C |
| 10 °Ré | 12.5 °C |
| 25 °Ré | 31.25 °C |
| 50 °Ré | 62.5 °C |
| 100 °Ré | 125 °C |
Methodology
Réaumur and Celsius are both interval temperature scales tied to fixed reference points (ice point and boiling point of water). Because the Réaumur scale sets water boiling at 80°Ré and Celsius at 100°C, the scales are related linearly.
This converter applies the exact scale factor derived from the fixed points. No empirical calibration or sensor corrections are applied by this tool. For traceable measurements, calibrate instruments per ISO/IEC 17025 and document measurement uncertainty as recommended by NIST and international metrology guidance.
Worked examples
0 °Ré → 0 °C (freezing point of water)
80 °Ré → 100 °C (boiling point of water at standard pressure)
12 °Ré → 15 °C (12 × 1.25 = 15)
Key takeaways
The conversion is exact and linear: multiply Réaumur by 1.25 to get Celsius.
Use this converter for quick arithmetic transformations. For any scientific, calibration, or compliance use, ensure instrument traceability and uncertainty reporting following metrology standards.
Further resources
External guidance
Expert Q&A
What is the Réaumur scale?
The Réaumur scale is a historical temperature scale where 0 °Ré is the freezing point of water and 80 °Ré is the boiling point of water at standard pressure. It is now rarely used but still appears in historical documents and some regional applications.
Why multiply by 1.25?
Because the Réaumur scale defines the boiling point of water as 80 units while Celsius defines it as 100 units; 100/80 = 1.25, so °C = °Ré × 1.25.
Is this conversion exact or approximate?
The numerical conversion between scales (°C = °Ré × 1.25) is exact as a mathematical relationship between the defined scales. Reported measurement values may carry instrument uncertainty that this converter does not estimate.
How should I handle measurement uncertainty and calibration?
For measurements used in research, manufacturing, or regulatory contexts, perform instrument calibration and uncertainty analysis. Follow ISO/IEC 17025 for laboratory competence and NIST guidance for temperature measurement and ITS-90 for temperature scale realization.
Are there limits where this conversion does not apply?
The linear conversion applies across the numeric range of both scales as defined. However, for extreme thermodynamic conditions where realization of the scale differs (very low or very high temperatures), consult metrology references and instrument specifications for validity and uncertainty.
Sources & citations
- NIST — Temperature and Thermometry (overview and ITS-90 resources) — https://www.nist.gov/pml/weights-and-measures/temperature
- ISO — ISO/IEC 17025: General requirements for the competence of testing and calibration laboratories — https://www.iso.org/standard/66912.html
- IEEE Standards Overview (sensor and instrumentation standards) — https://standards.ieee.org
- OSHA — General requirements for equipment calibration and maintenance guidance — https://www.osha.gov
- BIPM — International Bureau of Weights and Measures (metrology and units) — https://www.bipm.org