This paper is a complete overview of the reverse problem in the breakage matrix context. The procedure for calculating the input particle size distribution to a milling operation in order to obtain the desired output particle size distribution is given. The reverse problem was solved by the "precision" and "approximation" approaches. For the precision case, a detailed algorithm is presented, where in every step a precise range for the current output is provided. This approach is limited with a number of output size fractions that can be freely chosen. On the other hand, the approximation approach gives the best-fit solution which corresponds to the desired output particle size distribution. In this case the problem is solved by the orthogonal decomposition and non-negative least squares method and by semilogarithmic loss function. Applicability of the proposed methods was confirmed by examples related to wheat milling. (C) 2014 Elsevier B.V. All rights reserved.