What is degree Réaumur?

Degree Réaumur is a historical temperature scale where water freezes at 0° and boils at 80°. While largely obsolete, it was widely used in European science and medicine before the widespread adoption of Celsius.

Real-world uses

The Réaumur scale is largely obsolete but still appears in some European cheese-making and confectionery traditions, where specific Réaumur temperatures are cited in heritage recipes. It occasionally surfaces in historical scientific literature from 18th and 19th century Europe.

History

Devised by French scientist René Antoine Ferchault de Réaumur in 1730. It was widely used across continental Europe until the Celsius scale replaced it in the 19th century. Its 80-degree span between freezing and boiling was based on his alcohol thermometer design.

Common mistakes

Assuming the Réaumur scale is interchangeable with Celsius. While both set 0° at the freezing point of water, Réaumur sets boiling at 80° rather than 100°, so 1°Ré = 1.25°C.

What is degree Fahrenheit?

Degree Fahrenheit is a temperature unit primarily used in the United States for weather reports, cooking temperatures, and household settings. Water freezes at 32 °F and boils at 212 °F on this scale.

Real-world uses

Fahrenheit is the standard temperature unit in the United States for weather reports, oven settings, and body temperature (98.6°F normal). Some Caribbean nations and Liberia also use it. Pool and spa temperatures in the US are set in °F.

History

Daniel Gabriel Fahrenheit, a Polish-Dutch physicist, proposed this scale in 1724. He set 0°F as the temperature of a brine solution, 32°F as the freezing point of water, and 96°F as approximate body temperature. The scale was later adjusted slightly.

Common mistakes

Using the formula °F = °C × 2 + 30 as an exact conversion—it is only a rough estimate. The correct formula is °F = °C × 9/5 + 32. Also, assuming 0°F is absolute zero; it is actually about −17.8°C.

When is this conversion used?

This is the most common temperature conversion worldwide, needed for weather reports, cooking temperatures, and medical readings. Most of the world uses Celsius while the US primarily uses Fahrenheit.

Worked examples

1 degree Réaumur = -458.67 degree Fahrenheit

1 degree Fahrenheit = 0.55555556 kelvin

How to convert degree Réaumur to degree Fahrenheit

Temperature conversion uses a formula rather than a constant multiplier. The interactive converter above handles all calculations automatically.

Measurement standards

The kelvin is the SI base unit of thermodynamic temperature, defined by fixing the Boltzmann constant to exactly 1.380649 × 10⁻²³ joules per kelvin. This definition, adopted in 2019, decoupled the kelvin from the triple point of water.

Did you know?

The coldest temperature ever recorded on Earth was −89.2 °C (−128.6 °F) at the Soviet Vostok Station in Antarctica on 21 July 1983. In laboratories, scientists have cooled atoms to within billionths of a kelvin above absolute zero.

Quick reference: degree Réaumur to degree Fahrenheit

Common values

Available Temperature units

• degree Celsius conversions
• degree Fahrenheit conversions
• kelvin conversions
• degree Rankine conversions
• degree Réaumur conversions

More degree Réaumur conversions

• Convert degree Réaumur to degree Celsius
• Convert degree Réaumur to degree Fahrenheit
• Convert degree Réaumur to kelvin
• Convert degree Réaumur to degree Rankine

Assumption: formula-based scales using Kelvin as reference.