A uniform additive method (UAM) has been developed for calculating the thermodynamic functions heat capacity C (p) (T), enthalpy Delta H(T), entropy Delta S(T), and Gibbs free energy Delta G(T) of both individual organic compounds with known molecular structure and heavy feedstock, using elemental analysis and H-1 NMR data. The principle of the UAM is that a molecule or a unit mass of molecules of a mixture with a complex structure is represented as a unit mass of individual structural moieties (descriptors), which are transferable from one system to another. A comparison with the results of calculating the thermodynamic functions by other methods shows their satisfactory agreement, thereby giving promise that the UAM can be applied to complex systems.