Boltzmann constant

The Boltzmann constant (k or k_B) is a physical constant. It is defined to be 1.380649×10⁻²³ J/K.^[1] 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 N_A:

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

For the constant pertaining to energy of black body radiation see Stefan–Boltzmann constant

Values of k	Units
1.380649×10−23	J K−1
8.617333262×10−5	eV K−1
1.380649×10−16	erg K−1

The Boltzmann constant has SI units of J⋅K⁻¹ (also written J/K), the same as entropy. It is named after the Austrian physicist Ludwig Boltzmann.