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 kelvin?

Kelvin is the SI base unit of thermodynamic temperature, with its zero point at absolute zero. It is the standard in scientific and engineering fields where absolute temperature values are required, such as thermodynamics and astrophysics.

Real-world uses

Kelvin is the SI base unit for thermodynamic temperature, used in physics, chemistry, and engineering. Colour temperature of lighting (e.g., 5000 K daylight, 2700 K warm white) is specified in kelvins. Cryogenics and astrophysics rely on kelvin exclusively.

History

Named after William Thomson, 1st Baron Kelvin, who proposed an absolute temperature scale in 1848. The scale's zero point represents absolute zero, where molecular motion reaches its minimum. It became an SI base unit in 1954.

Common mistakes

Writing "degrees Kelvin" or "°K"—kelvin uses no degree symbol and is written simply as "K." Also, confusing kelvin with Celsius: 0 K is absolute zero (−273.15°C), not the freezing point of water.

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.

Worked examples

1 degree Réaumur = 0.55555556 kelvin

1 kelvin = 1 kelvin

How to convert degree Réaumur to kelvin

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 kelvin

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.