The problem of evaluating the life period of different mechanisms is of great importance nowadays. This could be explained by the fact that the wear process is very complex and many factors take place simultaneously. In the past decades a variety of theories that offered different wear calculation models were developed. However there is still no exact wear calculation model that could be applied to all cases of wear processes. The offered method is dealing with the calculation of rough surface peaks that make contact between two surfaces. Taking into account the number of these peaks and applying fatigue wear model to them in case of sliding-friction movement it is possible to make the wear calculation of friction pair under definite working conditions. The wear model is based on 3D surface micro-topography, assessing the material's physical and mechanical characteristic quantities and considering definite service conditions of sliding friction pair.