Kelvin

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Kelvin temperature conversion formulas
Conversion from to Formula
kelvins degrees Fahrenheit °F = K × 1.8 − 459.67
degrees Fahrenheit kelvins K = (°F + 459.67) / 1.8
kelvins degrees Celsius °C = K − 273.15
degrees Celsius kelvins K = °C + 273.15
Note that for temperature intervals rather than temperature readings,
1 K = 1 °C and 1 K = 1.8 °F
Additional conversion formulas
Conversion calculator for units of temperature

The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. It is defined by two facts: zero kelvins is absolute zero (when molecular motion stops), and one kelvin is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. The Celsius temperature scale is now defined in terms of the kelvin, with 0 °C corresponding to 273.15 kelvins, approximately the melting point of water under ordinary conditions.

The kelvin is named after the British physicist and engineer William Thomson, 1st Baron Kelvin.

In Unicode, a legacy code for a kelvin symbol to accommodate some old code pages in certain Oriental languages exists; it is not recommended for use any more. In all languages, the symbol should be the Roman letter Unicode K for current usage.

Typographical conventions

The word kelvin as an SI unit is correctly written with a lowercase k (unless at the beginning of a sentence), and is never preceded by the words degree or degrees, or the symbol °, unlike Fahrenheit, or Celsius. This is because the latter are scales of measurement, whereas the kelvin is a unit of measurement. It takes the normal plural form by adding an s in English: kelvins. When the kelvin was introduced in 1954 (10th Conférence Générale des Poids et Mesures|General Conference on Weights and Measures (CGPM), Resolution 3, CR 79), it was the "degree Kelvin", and written °K; the "degree" was dropped in 1967 (13th CGPM, Resolution 3, CR 104).

Note that the symbol for the kelvin unit is always a capital K and never italicised. There is a space between the number and the K, as with all other SI units.