Convert Fahrenheit to Réaumur
Convert degrees fahrenheit to degrees réaumur instantly. °Ré = (°F − 32) × 4/9 — use the live calculator, the exact formula, a reference-temperature table and worked examples. Also check the Réaumur to Fahrenheit converter for the reverse conversion.
Units explained
Fahrenheit
The degree Fahrenheit (°F) sets the freezing point of water at 32 °F and the boiling point at 212 °F, dividing the interval into 180 equal degrees. One degree Fahrenheit is exactly 5/9 the size of a kelvin, and °F = °C × 9/5 + 32 exactly.
Created by German-born physicist Daniel Gabriel Fahrenheit, inventor of the reliable mercury-in-glass thermometer. His zero point was the temperature of an ice-and-salt brine mixture, and his original upper fixed point sat near human body temperature.
The official everyday scale of the United States and a handful of other countries. In India, clinical thermometers and fever readings are still very commonly quoted in Fahrenheit (a '102-degree fever'), which keeps °F to °C conversion a daily need.
Introduced by Daniel Gabriel Fahrenheit in 1724 in Amsterdam, building directly on Ole Rømer's earlier scale, which Fahrenheit had studied during a 1708 visit to Copenhagen.
Réaumur
The degree Réaumur (°Ré) sets the freezing point of water at 0 °Ré and the boiling point at 80 °Ré, so one degree Réaumur equals exactly 1.25 kelvins (5/4 K).
Devised by French scientist René Antoine Ferchault de Réaumur using alcohol thermometers whose working liquid expanded 80 parts per thousand between the freezing and boiling points of water — the origin of the 80-degree span.
Once dominant across 18th- and 19th-century Europe, especially France, Germany, and Russia. It survives today mainly in traditional cheese-making — Parmigiano-Reggiano and Swiss alpine dairies still specify milk temperatures in °Ré.
Introduced by Réaumur in Paris in 1730; it faded from general use after France adopted the Celsius scale with the metric system in the 1790s.
Fahrenheit to Réaumur conversion formula
The exact relationship between degrees fahrenheit and degrees réaumur:
To convert degrees fahrenheit to degrees réaumur, subtract 32 from the value, then multiply by 4/9. To reverse, multiply the value by 9/4, then add 32.
Reference anchors: water freezes at 32 °F = 0 °Ré and boils at 212 °F = 80 °Ré (at standard atmospheric pressure).
How to use this converter
Type a value into the calculator. The result in degrees réaumur updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Réaumur to Fahrenheit converter for the reverse direction.
Step-by-step: convert degrees fahrenheit to degrees réaumur
- Write down the temperature in degrees fahrenheit (°F).
- Subtract 32 from the value, then multiply by 4/9.
- The result is the same temperature expressed in degrees réaumur (°Ré).
- To reverse, multiply the value by 9/4, then add 32 — or open the Réaumur to Fahrenheit converter.
Worked examples
Example 1 — Convert 98.6 °F to °Ré (human body temperature):
(98.6 − 32) × 4/9 = 29.6 °Ré
Example 2 — Convert 212 °F to °Ré (the boiling point of water):
(212 − 32) × 4/9 = 80 °Ré
Fahrenheit to Réaumur conversion table
Physically meaningful reference temperatures, from absolute zero to the surface of the Sun, converted from degrees fahrenheit to degrees réaumur:
| Fahrenheit [°F] | Réaumur [°Ré] | Reference point |
|---|---|---|
| -459.67 | -218.52 | Absolute zero |
| -40 | -32 | Where Celsius and Fahrenheit coincide (−40°) |
| 0 | -14.2222222222 | Zero Fahrenheit (0 °F) |
| 32 | 0 | Water freezes (0 °C / 32 °F) |
| 32.018 | 0.008 | Triple point of water |
| 50 | 8 | Cool day (10 °C / 50 °F) |
| 68 | 16 | Room temperature (20 °C / 68 °F) |
| 77 | 20 | Standard laboratory temperature (25 °C) |
| 86 | 24 | Hot day (30 °C / 86 °F) |
| 98.6 | 29.6 | Human body temperature (37 °C / 98.6 °F) |
| 104 | 32 | Heat-wave day (40 °C / 104 °F) |
| 122 | 40 | Hot tap water (50 °C / 122 °F) |
| 212 | 80 | Water boils (100 °C / 212 °F) |
| 356 | 144 | Moderate baking oven (180 °C / 356 °F) |
| 9940.73 | 4403.88 | Surface of the Sun (≈5,505 °C) |
Frequently asked questions
What is 98.6 °F in °Ré?
How do I convert degrees fahrenheit to degrees réaumur?
How do I convert degrees réaumur back to degrees fahrenheit?
At what temperature do the Fahrenheit and Réaumur scales read the same number?
Can a temperature be below absolute zero?
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Sources & references
Conversion relationship (°Ré = (°F − 32) × 4/9) verified against the following authoritative sources:
- BIPM — The International System of Units (SI Brochure 9th ed.)
Official BIPM publication defining the seven SI base units (including the meter) and the rules for their use. The global authority on units of measurement.
- NIST — Guide to the SI
US National Institute of Standards and Technology reference covering the SI base and derived units with definitions and usage rules for US technical practice.
- NIST Special Publication 811 — Guide for the Use of the International System of Units
Detailed NIST guide covering exact conversion factors between SI and US customary units along with formatting and rounding conventions.
- BIPM — International Temperature Scale of 1990 (ITS-90)
The internationally agreed practical temperature scale, defining fixed points (including the triple point of water at 273.16 K) and interpolation instruments used by national metrology institutes for thermometer calibration worldwide.
- CODATA Internationally Recommended Values of the Fundamental Physical Constants
Committee on Data of the International Science Council; authoritative source for the masses of fundamental particles (electron, proton, neutron) and the atomic mass constant.