# Boltzmann constant

For the constant pertaining to energy of black body radiation see Stefan–Boltzmann constant
Values of k[1] 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 the physical constant relating energy at the individual particle level with temperature, which can only be observed at the collective or bulk level. It is the gas constant R divided by the Avogadro constant NA:

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

It has the same units as entropy. It is named after the Austrian physicist Ludwig Boltzmann.

## References

1. 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