Kelvin Conversion Calculator

Kelvin Definition and Usage

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Joe Sexton

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The kelvin scale is used to measure temperature.

The kelvin is the SI base unit for temperature in the metric system. Kelvins can be abbreviated as K; for example, 1 kelvin can be written as 1 K.

What Is the Kelvin Scale?

The Kelvin scale is an absolute temperature scale that uses absolute zero as the starting point. The kelvin is defined in terms of the Boltzmann constant, which is a measure of the energy of motion corresponding to one kelvin.

More specifically, one kelvin is equal to the change of thermodynamic temperature that results in a change of thermal energy kT by 1.380649 × 10⁻²³ J.^[1]

0 kelvins are equal to −273.15 degrees Celsius, which is the point of absolute zero.

The kelvin scale is different from other temperature scales in that it is not expressed in degrees, values are expressed in kelvins. When using the Kelvin scale in writing, the "k" is capitalized, however when using the kelvin as a unit the "k" should be lower-case, even though it is named for a person.

Important Temperatures In Kelvins

Background and Origin

The kelvin is named for physicist William Thompson, who was enobled as Lord Kelvin, in recognition of his work in thermodynamics. Lord Kelvin suggested using an absolute temperature scale and later identified the value of absolute zero.

Uses

The Kelvin scale is widely used in the sciences and also has some everyday uses, such as measuring color temperature. The scale is used across the world for scientific measurements, including the United States which commonly uses the Fahrenheit scale for everyday use.