# Boltzmann formula

In statistical thermodynamics, the Boltzmann formula is an equation concerning the entropy S of a system derived from statistic or probability arguments:

$S = k \log W \!$

where k is the Boltzmann constant (Gas constant R divided by Avogadro’s number N) and W is the multiplicity or number of ways of describing the system. The Boltzmann formula, in quantitative terms, expresses the concept that entropy is a measure of disorder of a system. [1] The Boltzmann formula, in its modern form, was first given by German physicist Max Planck in 1901 as part of his principle of elementary disorder. [2]