Understanding the Boltzmann Constant

The Boltzmann constant (kB or k) is the proportionality factor that relates the average relative

thermal energy of particles in a gas with the thermodynamic temperature of the gas. It occurs in

the definitions of the kelvin (K) and the molar gas constant, in Planck's law

of black-body radiation and Boltzmann's entropy formula, and is used in calculating thermal noise in

resistors. The Boltzmann constant has dimensions of energy divided by temperature,

the same as entropy and heat capacity. It is named after the Austrian scientist Ludwig Boltzmann.

As part of the 2019 revision of the SI, the Boltzmann constant is one of the seven

"defining constants" that have been defined so as to have exact finite decimal values in SI units.