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 Rankine?

Degree Rankine is an absolute temperature scale based on Fahrenheit-sized degrees, where zero is absolute zero. It is used in engineering thermodynamics in the United States, particularly in aerospace and mechanical engineering calculations.

Real-world uses

The Rankine scale is used in some American engineering fields, particularly thermodynamics, combustion engineering, and heat transfer calculations where an absolute temperature in Fahrenheit-sized degrees is needed. It appears in US engineering textbooks and ASHRAE standards.

History

Named after Scottish-Irish engineer William John Macquorn Rankine, who proposed it in 1859. It serves as the Fahrenheit-scale analogue of kelvin. While kelvin uses Celsius-sized degrees from absolute zero, Rankine uses Fahrenheit-sized degrees from absolute zero.

Common mistakes

Confusing Rankine with Fahrenheit—Rankine starts at absolute zero (0°R = −459.67°F), not at 0°F. Also, forgetting that the conversion from Fahrenheit is simply °R = °F + 459.67.

When is this conversion used?

Converting degree Réaumur to degree Rankine 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 = 1 degree Rankine

1 degree Rankine = 0.55555556 kelvin

How to convert degree Réaumur to degree Rankine

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 Rankine

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.