degree Réaumur (°Re)

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.

Notes: K = °Re * 1.25 + 273.15

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.

When is this conversion used?

Converting degree Réaumur to kelvin is useful in the temperature domain when comparing values across different measurement standards or applying formulas that require a specific unit.

How to convert degree Réaumur to kelvin

Formula: K = °Re × 1.25 + 273.15

Conversion formula (from base unit)

(x * 1.25 + 273.15)

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.

Common values

Full degree Réaumur conversion table

Other Temperature units

View all Temperature conversions

• degree Celsius
• degree Fahrenheit
• kelvin
• degree Rankine