The paper features the mathematical model of computing thermophysical prope
rties in the liquid, gas and two phase domain with the help of statistical
thermodynamics. To calculate the thermodynamic properties of real gases we
developed the cluster theory which yields better results than the virial eq
uation. For the realm of real liquids the Johnson-Zollweg-Gubbins model was
applied. The Lennard-Jones intermolecular potential was used.