The Boltzmann constant is symbolized by the letter "k" or the letter combination "kB". It defines the ratio between the absolute temperature in Kelvin and the kinetic energy contained in each individual molecule, ideally a gas molecule. The Boltzmann constant has a fixed value of 1.380650 x 10exp-23 joules/ kelvin. The energy in a gas molecule is proportional to the absolute temperature. If the temperature increases, then the kinetic energy of any molecule increases.