AbstractThe paper presents an approach for construction of optimal size ranges of modules for building technical products. The necessary input data are the demand (needs) function, defined for modules with known values of their main parameters, and the functional relationship between a chosen optimality criterion (total discounted costs for the service life of the size range) and the influencing factors. The approach includes a study of the optimality criterion's sensitivity towards the input data. The optimal size range provides minimum total costs while satisfying a known demand function. It is a compromise solution between the contradicting interests of manufacturers, for minimum number of sizes, and users, wanting large number of sizes. For finding the optimal size range, utilization of a suitable mathematical method for optimization is proposed, which method recognizes the characteristic features of the solved problem - discrete nature and large number of variants that have to be analyzed.