In the article a method of the degree of utilization of plasticity source definition for a workpiece material in a forging on the radial-forging machine is proposed. This allows to conduct technological processes of a rod forging on the radial forging machine with an appropriate workpiece reduction value.The research that has been made included both theoretical and experimental parts. The theoretical part consists of a definition of stress state during deformation according to the developed mathematical model, values of shear strain and plasticity of metal and also a degree of utilization of plastic source during the process. Also an experiment in which a rod forging was carried out with known values of reduction in each transition has been made.For the purpose of a model verification a comparison between data from modelling and experimental results on the forging of rods made from different alloys has been done.