Kelvin

Categories: Accuracy disputes | SI base units | Units of temperature

For other uses, see Kelvin (disambiguation).

**Kelvin temperature conversion formulas**
Conversion from	to	Formula
kelvins	degrees Celsius	°C = K − 273.15
degrees Celsius	kelvins	K = °C + 273.15
kelvins	degrees Fahrenheit	°F = K × 1.8 − 459.67
degrees Fahrenheit	kelvins	K = (°F + 459.67) / 1.8
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 as the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.

A temperature given in kelvins, without further qualification, is measured with respect to absolute zero, where molecular motion stops. It is also common to give a temperature relative to the reference temperature of 273.15 K, approximately the melting point of water under ordinary conditions; this convention is the Celsius temperature scale.

The kelvin is named after the British physicist and engineer William Thomson, 1st Baron Kelvin; his barony was in turn named after the River Kelvin, which runs through the grounds of the University of Glasgow.

1 Typographical conventions
2 Conversion factors
- 2.1 Kelvins and Celsius
- 2.2 Temperature and energy
3 SI multiples
4 See also
5 External link

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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 degrees Fahrenheit, or degrees Celsius. This is because the latter are adjectives, whereas kelvin is a noun. It takes the normal plural form by adding an s in English: kelvins. When the kelvin was introduced in 1954 (10th 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.

Unicode includes the "kelvin sign" at U+212A (in your browser it looks like K). However, the "kelvin sign" is canonically decomposed into U+004B, thereby seen as a (preexisting) encoding mistake, and it is better to use U+004B (K) directly.

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Conversion factors

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Kelvins and Celsius

The Celsius temperature scale is now defined in terms of the kelvin, with 0 °C corresponding to 273.15 kelvins.

kelvins to degrees Celsius
<math>

\mathrm{C} = \mathrm{K} - 273.15 </math>

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Temperature and energy

Image:Stop hand.png

The factual accuracy of this article is disputed.

Please see the relevant discussion on the talk page.

In a thermodynamic system, the energy carried by the particles is proportional to the absolute temperature, where the constant of proportionality is the Boltzmann constant. As a result, it is possible to determine the temperature of particles with a certain energy; or to calculate the energy of particles at a certain temperature:

<math>

\overline{\mathrm{E_{kin}}} = \frac{3}{2} \cdot k_B \cdot \mathrm{T} </math>

electron volts to kelvins

<math>

\mathrm{K} = \mathrm{eV} \times 11,\!605 </math>

kelvins to electron volts

<math>

\mathrm{eV} = \frac{\mathrm{K}}{11,\!605} </math>

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SI multiples

Multiple	Name	Symbol	Multiple	Name	Symbol
10⁰	kelvin	K
10¹	decakelvin	daK	10^–1	decikelvin	dK
10²	hectokelvin	hK	10^–2	centikelvin	cK
10³	kilokelvin	kK	10^–3	millikelvin	mK
10⁶	megakelvin	MK	10^–6	microkelvin	µK
10⁹	gigakelvin	GK	10^–9	nanokelvin	nK
10¹²	terakelvin	TK	10^–12	picokelvin	pK
10¹⁵	petakelvin	PK	10^–15	femtokelvin	fK
10¹⁸	exakelvin	EK	10^–18	attokelvin	aK
10²¹	zettakelvin	ZK	10^–21	zeptokelvin	zK
10²⁴	yottakelvin	YK	10^–24	yoctokelvin	yK