Conversions

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Conversions

Réaumur to Fahrenheit Calculator.

Converts a temperature from the Réaumur scale to Fahrenheit, showing the equivalent in Celsius as well.

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How it works

  1. 1

    Enter the temperature in degrees Réaumur.

  2. 2

    Multiply the Réaumur value by 9/4 (or 2.25).

  3. 3

    Add 32 to the result to get degrees Fahrenheit.

  4. 4

    The calculator also shows the Celsius equivalent (Réaumur × 5/4).

reaumur * 9 / 4 + 32

Frequently asked questions

What is the Réaumur scale?

The Réaumur scale sets the freezing point of water at 0°Ré and the boiling point at 80°Ré. It was used in Europe in the 18th–19th centuries.

How do I convert Fahrenheit to Réaumur?

Use the inverse formula: Réaumur = (Fahrenheit - 32) × 4/9.

Why is the conversion factor 9/4?

Because 80°Ré corresponds to 180°F between freezing and boiling, so 1°Ré = 180/80 = 9/4 °F.

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Temperature

0°F

Celsius0°C
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How it works

Converts a temperature from the Réaumur scale to Fahrenheit, showing the equivalent in Celsius as well.

  1. Enter the temperature in degrees Réaumur.
  2. Multiply the Réaumur value by 9/4 (or 2.25).
  3. Add 32 to the result to get degrees Fahrenheit.
  4. The calculator also shows the Celsius equivalent (Réaumur × 5/4).

Formulas

The math behind this calculator, written out so you can verify the result.

Réaumur to Fahrenheit

°F = °Ré × 9/4 + 32

Multiply the Réaumur temperature by 9/4 (the ratio of Fahrenheit degrees per Réaumur degree) and add 32 to shift the freezing point.

Example:

Input: °Ré = 20

Calculation: 20 × 9/4 + 32 = 45 + 32

Result: 77°F

Réaumur to Celsius

°C = °Ré × 5/4

Since 80°Ré equals 100°C, each Réaumur degree is 5/4 of a Celsius degree.

Example:

Input: °Ré = 20

Calculation: 20 × 5/4 = 25

Result: 25°C

Real-world use cases

Where this calculation shows up in everyday life.

Historical temperature records

Convert old European scientific or weather data recorded in Réaumur to modern Fahrenheit or Celsius.

Example: A 19th-century journal lists 30°Ré; convert to 99.5°F.

Cooking with antique recipes

Some vintage cookbooks use Réaumur for oven temperatures; convert to Fahrenheit for modern ovens.

Example: A recipe says 25°Ré, which is 88.25°F.

Education and science

Help students understand temperature scales and conversion factors.

Example: Show that 0°Ré = 32°F and 80°Ré = 212°F.

Tips and common mistakes

Tips

  • Remember the freezing point of water: 0°Ré = 32°F.
  • For quick mental estimates, multiply by 2 and add 30 (slightly overestimates).
  • Use the Celsius conversion as an intermediate step if you prefer: °F = (°Ré × 5/4) × 9/5 + 32.

Common Mistakes to Avoid

  • Forgetting to add 32 after multiplying by 9/4.
  • Using 5/4 instead of 9/4 for the Fahrenheit conversion.
  • Confusing Réaumur with Rankine or other obscure scales.

Assumptions and limitations

  • Use the stated inputs and units.
  • Results are estimates for planning and education.
  • Check measurements and source data before making an important decision.