This paper covers theoretical and experimental explorations for the sake of determining the optimal ball charge in mills. In the first part of the paper, on the basis of the theoretical analysis of the energy-geometric correlations, which are being established during the grain comminution by ball impact, as well as on the basis of the experiment carried out on grinding quartz and copper ore in a laboratory ball mill, there has been defined a general form of the equation for determining: the optimal ball diameter depending on the grain size being ground; and the parameter of the equation through which the influence of a mill is being demonstrated; then the parameter of the grinding conditions; and the parameter of the material characteristics being ground in relation to the ball size. In the second part of the paper, the process of making up the optimal ball charge has been defined providing the highest grinding efficiency, as well as its confirmation by the results of the experimental explorations.