Convert Kelvin to Celsius (2024)

Please provide values below to convert kelvin [K] to Celsius [°C], or vice versa.

Kelvin

Definition: The kelvin (symbol: K) is the base unit of thermodynamic temperature in the International System of Units (SI). It is defined as the energy equivalent of the triple point of water as given by Boltzmann's equation. It is also the unit of the Kelvin scale in which the null point (0 K) is the temperature at which all thermal motion ceases, known as absolute zero, or -273.15°C. The definition of the kelvin was changed in 2019. This new definition results in a fundamental change in the kelvin, such that it is now dependent on the definitions of the second, the meter, and the kilogram.

History/origin: The kelvin is named after British physicist William Thomson, who was known as Lord Kelvin. Thomson wrote a paper outlining the need for an absolute temperature scale. He calculated the value of absolute zero to be -273°C in 1848 which is only a 0.15°C deviation from the current accepted value.

Until late 2018, the kelvin was defined as 1/273.16 of the thermodynamic temperature of the triple point of water (0.01°C or 32.018°F). This definition came about in 1954, when the General Conference on Weights and Measures designated the triple point of water as the second defining point of the Kelvin scale, defining the temperature as exactly 273.16 K.

Although the definition of the kelvin has changed fundamentally in 2019, it does not affect how the kelvin is used, or its relationship to other temperature scales and units.

Current use: The kelvin is used worldwide, particularly in science and engineering, together with the Celsius. This is partially due to the kelvin and the Celsius degree having exactly the same magnitude. Unlike the Celsius and Fahrenheit, the kelvin is not used in meteorological contexts.

Celsius

Definition: The Celsius (symbol: °C) is an SI (International System of Units) derived unit of temperature. It is defined based on the SI unit of temperature, the kelvin. The Celsius and Kelvin scales are precisely related, with a one-degree change in Celsius being equal to a one degree-change in kelvin. The kelvin (and thus Celsius) is defined based on the Boltzmann constant, k, which equals 1.380649 × 10^-23 when expressed in the unit J·K^-1, a unit equivalent to kg·m²·s^-2·K^-1. The kilogram, meter, and second, are defined based on Planck's constant, h, the speed of light, c, and cesium frequency, ΔνCs.

History/origin: From 1743 until 1954, the Celsius scale was based on 0°C for the freezing point of water and 100 °C for the boiling point of water, both at a pressure of one standard atmosphere, using mercury as the working material. This was not always the case, and originally 0°C was defined as the boiling point of water and 100°C was defined as the melting point of snow. Celsius as a unit and a scale was not widely used until this original definition was inverted. In 1954, the unit, "degree Celsius," as well as the Celsius scale were again re-defined to instead be based on absolute zero (-273.15 °C) and the triple point of VSMOW (specially purified water). This is the definition that was used up until 2019, when the kelvin was redefined based on the definitions of the second, meter, and kilogram.

Current use: The Celsius scale replaced the Fahrenheit scale in most countries in the mid to late 20^th century. Almost all countries around the world use this scale, except for those in which the metric system has not been adopted, such as the United States. Even in countries like the United States however, Celsius is widely used within the scientific community—it just is not widely used in everyday temperature references.

Kelvin to Celsius Conversion Table

How to Convert Kelvin to Celsius

C = K - 273.15
K = C + 273.15

Example: convert 300 K to °C
300 K = 300 - 273.15 = 26.85 °C

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