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.

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 between kelvin and degree Rankine is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region.

Worked examples

1 kelvin = 1.8 degree Rankine

1 degree Rankine = 0.55555556 kelvin

How to convert kelvin 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: kelvin to degree Rankine

Common values

Available Temperature units

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

More kelvin conversions

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

Assumption: formula-based scales using Kelvin as reference.