Réaumur (°Ré)
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Equivalent temperature
Accurate °C to °Ré temperature conversion with full multi-scale breakdowns
Convert Celsius to Réaumur instantly with precise calculations. Includes bidirectional conversion and complete temperature scale breakdowns including Fahrenheit, Kelvin, and Rankine for 2026.
Professional temperature conversion for science, history, and culinary applications
Convert Celsius to Réaumur using the exact factor: °Ré = °C × 0.8. The Réaumur scale sets water's freezing point at 0°Ré and boiling point at 80°Ré, making the conversion from Celsius straightforward and precise for any temperature value in 2026.
Switch seamlessly between Celsius to Réaumur and Réaumur to Celsius conversion modes. Every result includes a complete temperature breakdown across Fahrenheit, Kelvin, and Rankine scales — giving you the full picture from a single input value.
The Réaumur scale is encountered in historical scientific literature, European culinary traditions (particularly French and Italian confectionery), and antique thermometer collections. Our converter bridges historical and modern temperature measurement systems accurately for researchers, chefs, and collectors in 2026.
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The Réaumur scale (°Ré) is one of the earliest standardised temperature scales, invented by the French scientist René Antoine Ferchault de Réaumur in 1730. It sets 0°Ré as the freezing point of water and 80°Ré as the boiling point of water at standard atmospheric pressure — compared to Celsius which uses 0°C and 100°C for the same points. Because the Réaumur scale divides the same temperature interval into 80 degrees rather than 100, the conversion factor is simply 4/5 (0.8): multiply Celsius by 0.8 to get Réaumur.
While the Réaumur scale is no longer in everyday scientific use, it remains relevant in historical research, European culinary traditions, and antique instrument study. French and Italian confectionery recipes — particularly for sugar work and candy making — traditionally use Réaumur temperatures for sugar syrup stages. Historical European scientific texts from the 18th and 19th centuries also frequently reference Réaumur temperatures, making accurate conversion tools essential for researchers in 2026.
Example: 100°C × 0.8 = 80°Ré | 25°C × 0.8 = 20°Ré | 40°Ré × 1.25 = 50°C
Water boiling point: 100°C = 80°Ré = 212°F = 373.15 K = 671.67°R | Freezing point: 0°C = 0°Ré = 32°F = 273.15 K
Use the reference table below to quickly look up common Celsius to Réaumur conversions, including equivalent Fahrenheit and Kelvin values for full context across all major temperature scales.
| Celsius (°C) | Réaumur (°Ré) | Fahrenheit (°F) | Kelvin (K) | Description |
|---|---|---|---|---|
| −40°C | −32°Ré | −40°F | 233.15 K | Extreme cold |
| −20°C | −16°Ré | −4°F | 253.15 K | Very cold winter |
| −10°C | −8°Ré | 14°F | 263.15 K | Cold winter day |
| 0°C | 0°Ré | 32°F | 273.15 K | Water freezing point |
| 10°C | 8°Ré | 50°F | 283.15 K | Cool day |
| 20°C | 16°Ré | 68°F | 293.15 K | Room temperature |
| 25°C | 20°Ré | 77°F | 298.15 K | Warm room |
| 37°C | 29.6°Ré | 98.6°F | 310.15 K | Human body temperature |
| 40°C | 32°Ré | 104°F | 313.15 K | Hot summer day |
| 60°C | 48°Ré | 140°F | 333.15 K | Hot water |
| 100°C | 80°Ré | 212°F | 373.15 K | Water boiling point |
| 200°C | 160°Ré | 392°F | 473.15 K | Oven temperature |
The Celsius-to-Réaumur conversion is one of the simplest temperature conversions because both scales share the same zero point — the freezing point of water at 0°. The only difference is the scale interval: Celsius divides the boiling-to-freezing range into 100 degrees, while Réaumur divides it into 80 degrees. This 80/100 = 4/5 = 0.8 ratio is the entire conversion formula. No offset is needed, unlike Fahrenheit conversions.
°C → °Ré: Multiply by 0.8 (e.g., 25°C × 0.8 = 20°Ré)
°Ré → °C: Multiply by 1.25 (e.g., 20°Ré × 1.25 = 25°C)
Key anchors: 0°C = 0°Ré | 100°C = 80°Ré | 37°C = 29.6°Ré
From °Ré to °F: °F = (°Ré × 2.25) + 32
Although the Réaumur scale was officially displaced by the Celsius scale in most of Europe during the 19th century, it survives in specific contexts. European confectionery — particularly French pâtisserie and Italian candy making — has traditionally used Réaumur temperatures to define sugar syrup cooking stages. Historical European weather records, scientific papers from the 1700s to mid-1800s, and antique mercury thermometers often carry Réaumur calibrations, making conversion tools essential for historians, archivists, and collectors.
Traditional French and Italian recipes for confectionery, jam, and sugar work use Réaumur temperatures. The "soft ball" stage of sugar is around 116°C (92.8°Ré), hard crack is approximately 150°C (120°Ré). Chefs and pastry historians working from period recipes regularly need to convert Réaumur temperatures to Celsius or Fahrenheit for modern kitchen use in 2026.
European scientific literature from the 18th and 19th centuries — including works by Lavoisier, Linnaeus, and early meteorologists — commonly recorded temperatures in Réaumur. Researchers translating or analysing these primary sources need accurate Réaumur-to-Celsius conversion to contextualise temperature data within modern scientific frameworks.
Antique thermometers from France, Germany, and Italy are commonly calibrated in Réaumur. Collectors and museum curators working with 18th and 19th century scientific instruments need to convert Réaumur readings to Celsius for condition reports, exhibition labels, and provenance documentation of historical artefacts.
19th-century European novels, travel accounts, and diaries frequently reference outdoor temperatures in Réaumur. Famous works by Tolstoy and other Russian and European authors mention Réaumur temperatures when describing weather. Literary scholars and translators converting these references into modern equivalents need a reliable °Ré to °C tool.
The Celsius and Réaumur scales share the same zero point (the freezing point of water = 0° on both scales), but differ in their upper anchor and degree size. On the Celsius scale, water boils at 100°C, while on the Réaumur scale it boils at 80°Ré. This means each Réaumur degree is 1.25 times larger than a Celsius degree — so Réaumur values are always smaller numbers than the equivalent Celsius value for temperatures above zero, and larger (more negative) for sub-zero temperatures.
Freezing point of water: 0°C = 0°Ré (identical)
Boiling point of water: 100°C = 80°Ré
Human body temperature: 37°C ≈ 29.6°Ré
Room temperature (20°C): 20°C = 16°Ré
Degree size: 1°Ré = 1.25°C — each Réaumur degree is larger than a Celsius degree
The symbol °R is sometimes used for both Réaumur and Rankine — two completely different temperature scales. Réaumur (°Ré) is a historical European scale where water freezes at 0° and boils at 80°. Rankine (°Ra or °R) is an absolute thermodynamic scale used in engineering, where absolute zero = 0°Ra and water freezes at 491.67°Ra. Always confirm which scale is intended when you see the symbol °R in older texts or engineering documents.
The Réaumur scale is one of several historical temperature scales alongside Fahrenheit, Delisle, Newton, and Rømer. Understanding these historical systems is essential for researchers working with 18th and 19th century European scientific literature, weather records, and medical documents in 2026.
Explore All Converters →Traditional European confectionery recipes use Réaumur temperatures for sugar stages. Our converter helps modern chefs and bakers translate historical recipe temperatures into Celsius and Fahrenheit values for accurate reproduction of classic French and Italian sweets and pastries.
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