A new method of modelling comminution processes is introduced. The function responsible for the description of the particle size reduction is thought to be a random one. It is calculated by maximizing an informational entropy. The energy for the comminution process is described by Rittinger's or Kick's law. One model fitting parameter is necessary. It can be estimated from measured product size distributions. In addition to the prediction of product size distributions, the model is able to show the influence of the energy input to the single feed fractions as well as to predict this energy split function.