Instantly Convert °F to °Ré or Réaumur to Fahrenheit — Both Directions
Convert Fahrenheit to Réaumur (°F → °Ré) or Réaumur to Fahrenheit (°Ré → °F) instantly. Get the exact conversion with formula breakdown, reference table, and related temperature conversions — all free, no sign-up needed.
Fahrenheit and Réaumur are two historical temperature scales that both anchor on the freezing point of water — but divide the range to boiling differently. Our converter handles both directions instantly using the exact conversion formula with no rounding.
The Fahrenheit scale (°F) was proposed by German physicist Daniel Gabriel Fahrenheit in 1724. It defines the freezing point of water as 32°F and the boiling point as 212°F at standard atmospheric pressure — a span of 180 Fahrenheit degrees. It remains the everyday temperature scale in the United States.
The Réaumur scale (°Ré) was proposed by French scientist René Antoine Ferchault de Réaumur in 1730. It sets the freezing point of water at 0°Ré and the boiling point at 80°Ré — dividing this range into 80 equal parts. Once widely used across Europe, the Réaumur scale is now largely obsolete but still appears in some European cheese-making and historical contexts.
The Fahrenheit scale spans 180 degrees between freezing and boiling, while Réaumur spans only 80 degrees for the same range. This gives a ratio of 9:4 (180 ÷ 80 = 2.25). Because Fahrenheit also has an offset of 32°F at the freezing point, the formula is: °Ré = (°F − 32) × 4/9.
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The conversion between Fahrenheit and Réaumur requires both a degree-size adjustment and an offset correction. The Fahrenheit scale starts at 32°F at the freezing point, while Réaumur starts at 0°Ré — so the 32-degree offset must be subtracted first. The remaining difference is then scaled by the ratio 4/9 (since 80°Ré = 180°F between freezing and boiling).
The figure below shows key reference temperatures side by side on the Fahrenheit and Réaumur scales. Notice that both scales anchor at the freezing point of water — 32°F = 0°Ré — and that Réaumur numbers are always smaller than their Fahrenheit equivalents above freezing due to the 4/9 scaling ratio.
The table below lists a wide range of Fahrenheit values converted to Réaumur using the exact formula °Ré = (°F − 32) × 4/9. Celsius and Kelvin equivalents are included for full temperature context and easy cross-reference.
| Fahrenheit (°F) | Réaumur (°Ré) | Celsius (°C) | Kelvin (K) | Reference Point |
|---|---|---|---|---|
| −40°F | −32°Ré | −40°C | 233.15 K | °F = °C crossover point |
| 0°F | −14.22°Ré | −17.78°C | 255.37 K | Fahrenheit zero |
| 14°F | −8°Ré | −10°C | 263.15 K | Cold winter temperature |
| 32°F | 0°Ré | 0°C | 273.15 K | Water freezing point |
| 41°F | 4°Ré | 5°C | 278.15 K | Cold spring morning |
| 50°F | 8°Ré | 10°C | 283.15 K | Cool weather |
| 59°F | 12°Ré | 15°C | 288.15 K | Mild temperature |
| 68°F | 16°Ré | 20°C | 293.15 K | Standard room temperature |
| 72°F | 17.78°Ré | 22.22°C | 295.37 K | Comfortable indoor temp |
| 77°F | 20°Ré | 25°C | 298.15 K | Warm room / standard ref |
| 86°F | 24°Ré | 30°C | 303.15 K | Hot summer day |
| 98.6°F | 29.6°Ré | 37°C | 310.15 K | Normal human body temp |
| 104°F | 32°Ré | 40°C | 313.15 K | High fever threshold |
| 122°F | 40°Ré | 50°C | 323.15 K | Extreme heat |
| 176°F | 64°Ré | 80°C | 353.15 K | Near boiling — hot liquids |
| 212°F | 80°Ré | 100°C | 373.15 K | Water boiling point |
| 392°F | 160°Ré | 200°C | 473.15 K | Oven baking temperature |
| 1000°F | 432°Ré | 537.78°C | 810.93 K | Industrial furnace range |
The table below converts common Réaumur values back to Fahrenheit using the formula °F = (°Ré × 9/4) + 32. This is useful when working with historical European records or traditional recipes that reference the Réaumur scale.
| Réaumur (°Ré) | Fahrenheit (°F) | Celsius (°C) | Kelvin (K) |
|---|---|---|---|
| −32°Ré | −40°F | −40°C | 233.15 K |
| −14.22°Ré | 0°F | −17.78°C | 255.37 K |
| 0°Ré | 32°F | 0°C | 273.15 K |
| 4°Ré | 41°F | 5°C | 278.15 K |
| 8°Ré | 50°F | 10°C | 283.15 K |
| 16°Ré | 68°F | 20°C | 293.15 K |
| 20°Ré | 77°F | 25°C | 298.15 K |
| 24°Ré | 86°F | 30°C | 303.15 K |
| 29.6°Ré | 98.6°F | 37°C | 310.15 K |
| 32°Ré | 104°F | 40°C | 313.15 K |
| 40°Ré | 122°F | 50°C | 323.15 K |
| 60°Ré | 167°F | 75°C | 348.15 K |
| 80°Ré | 212°F | 100°C | 373.15 K |
| 100°Ré | 257°F | 125°C | 398.15 K |
| 160°Ré | 392°F | 200°C | 473.15 K |
While the Réaumur scale is largely obsolete in modern science, it still appears in specific historical, culinary, and academic contexts. Here are the most common situations where this conversion is needed.
The Réaumur scale has survived longest in traditional European food and dairy production — particularly in parts of Italy, Germany, and Russia. Some historical and artisan cheese-making recipes specify temperatures in Réaumur. For example, curd heating at 34–36°Ré (95–104.75°F) is a common reference in traditional Parmesan and Alpine cheese production.
Many scientific papers, weather records, and natural philosophy texts from the 18th and 19th centuries — especially from France, Germany, and Russia — recorded temperatures in Réaumur. Researchers studying historical climate data or translating period scientific work regularly need to convert Réaumur readings to modern Fahrenheit or Celsius equivalents.
Classic European literature and historical accounts frequently mention temperatures in Réaumur. Works by Tolstoy, Goethe, and other 18th–19th century authors reference weather in °Ré. Historians, translators, and literature scholars converting these references for modern readers need a reliable Fahrenheit to Réaumur converter to provide accurate modern equivalents. This also pairs with understanding energy unit conversions from the same historical era.
Students studying the history of thermometry and temperature measurement encounter the Réaumur scale as part of understanding how modern scales developed. Comparing Fahrenheit, Celsius, Kelvin, Rankine, and Réaumur — their origins, degree sizes, and anchor points — is a common topic in physics and science history curricula. Understanding °Ré = (°F − 32) × 4/9 reinforces proportional reasoning and unit conversion skills.
Early European meteorological stations recorded air and water temperatures in Réaumur throughout the 1700s and 1800s. Climatologists and historians digitising these records must convert Réaumur values to Celsius or Fahrenheit for modern climate analysis. A summer temperature of 20°Ré = 77°F = 25°C gives a clear picture when the original scale is properly understood and converted.
Traditional European brewing and distilling records — particularly from Germany, Austria, and Russia — sometimes reference Réaumur for mash temperatures and fermentation ranges. A mash temperature of 40–44°Ré (122–131°F) corresponds to optimal enzyme activity in brewing. Modern brewers working from historical recipes need to convert these values to Fahrenheit or Celsius for their contemporary equipment.
Learn about René Antoine Ferchault de Réaumur and the development of his temperature scale in 1730 — including why he chose 80 divisions and how the scale was adopted across 18th-century Europe before being replaced by Celsius.
Read on Wikipedia →The National Institute of Standards and Technology provides authoritative reference data on temperature scales, SI units, and the International Temperature Scale (ITS-90) used as the modern global standard for temperature measurement.
Visit NIST →Need to convert between Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur all at once? Explore the full suite of unit conversion tools on ConcreteMetric for fast, accurate results across all measurement types.
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