Kelvin K
About the Kelvin
The kelvin is defined by fixing the Boltzmann constant at exactly 1.380649 × 10⁻²³ joules per kelvin. Before 2019 it was 1/273.16 of the thermodynamic temperature of the triple point of water. Zero kelvin is absolute zero, and a temperature difference of one kelvin equals one degree Celsius. It is named after William Thomson, Lord Kelvin, and is written without the word degree.
Related Units
Degree Celsius
°Ct/°C = T/K − 273.15
The degree Celsius is equal in size to the kelvin, but its scale is offset so that 0 °C is 273.15 K. It is named after...
Degree Fahrenheit
°F°F = °C × 9/5 + 32
Daniel Gabriel Fahrenheit proposed his scale in 1724. On it water freezes at 32 °F and boils at 212 °F at standard...
Metre
mBase unit; c = 299,792,458 m/s exactly
The metre is the length of the path travelled by light in vacuum in 1/299,792,458 of a second. It was first defined by...
Kilogram
kgBase unit; h = 6.62607015 × 10⁻³⁴ J·s exactly
The kilogram is defined by fixing the Planck constant at exactly 6.62607015 × 10⁻³⁴ joule-seconds. Until 20 May 2019 it...