# Boltzmann constant

For the constant pertaining to energy of black body radiation see Stefan–Boltzmann constant
Values of k[2] Units
1.3806488(13)×10−23 JK−1
8.6173324(78)×10−5 eV K−1
1.3806488(13)×10−16 erg K−1

The Boltzmann constant (k or kB) is a physical constant. It relates the average kinetic energy of a particle in a gas with the temperature of the gas. It is the gas constant R divided by the Avogadro constant NA:

${\displaystyle k={\frac {R}{N_{\rm {A}}}}\,}$

The Boltzmann constant has SI units of JK−1, the same as entropy. It is named after the Austrian physicist Ludwig Boltzmann. "Although Boltzmann published his famous definition of entropy in 1877, the constant of proportionality in Boltzmann’s definition, was not identified as Boltzmann’s constant until 1900 when Planck published his analysis of blackbody radiation (1900a, 1900b), where he identified the constant as and named it after Boltzmann."

## References

1. "When did the name "Boltzmann constant" prevail, and how?". History of Science and Mathematics Stack Exchange. Retrieved 2018-09-28.
2. P.J. Mohr, B.N. Taylor, and D.B. Newell (2011), "The 2010 CODATA Recommended Values of the Fundamental Physical Constants" (Web Version 6.0). This database was developed by J. Baker, M. Douma, and S. Kotochigova. Available: http://physics.nist.gov/constants [Thursday, 02-Jun-2011 21:00:12 EDT]. National Institute of Standards and Technology, Gaithersburg, MD 20899. Archived 21 February 2012 at WebCite