The article presents a method of discretising a belt used in a transmission model with any number of pulleys and tensioning rollers and any direction of wrapping the pulleys or rollers. The positions of the discretising points are formulated in a global coordinate system. The method allows for arbitrary placement of pulleys and tensioning rollers. It also consequently allows to calculate the length of the belt, resulting from the geometry of the transmission, and the length of the belt, resulting from the coordinates of the discretising points that lie on its circumference. The method presented here allows to estimate the number of points that would provide satisfactory accuracy of the belt’s curvature surrounding the individual pulleys and rollers. In the paper presented comparison between two proposed ways of estimating. Designated points can be used as input data to analyse the belt dynamics with the belt modelled as rigid elements connected to one another by translational or rotational spring-damping elements.