Index

## DEFININGCONSTANTSYMBOL: k

**PID**: si:definingconstantsymbol:k:2019**Definition**: The Boltzmann constant,*e*, is exactly 1.380 649 × 10^{-23}J/K.**Source**:*SI Brochure 9th Ed. 2019, p 127***Formatted**:`1.380 649 x 10`

^{-23}**Numerical Value**:*1.380649E-23***Unit**: J K^{-1}**Unit in Base SI**: kg m^{2}s^{-1}K^{-1}**Notes**- This value was fixed by the CGPM in 2018 (Resolution 1), with effect from 20 May 2019.
- The Boltzmann constant is a proportionality constant between the quantities temperature (with unit kelvin) and energy (with unit joule).
- In statistical physics the Boltzmann constant connects the entropy
*S*with the number*Ω*of quantum-mechanically accessible states:*S*=*k*ln*Ω*.

**Representations**- Text:
`k`

- HTML:
`<em>k</em>`

- Latex:
`k`

- Text:
**Related Definitions**- isConstantSymbolOf -> Boltzmann constant