Oxidizer and fuel particles are the ingredients of classical pyrotechnics. Particle concentration, size, melting, evaporation, and decomposition of the particles, heat and mass transfer, reaction kinetics, and heat of reaction control the burning behavior of these mixtures. A hot-spot approach models the reaction progress in three dimensions taking into consideration the particulate nature of pyrotechnic compositions. The governing reaction is assumed to be the oxidizer decomposition described by an Avrami-Erofeev model. Predominantly, the distribution of the oxidizer and fuel particles and their size for various concentrations influence the burning rate beneath the reaction kinetic parameters. The computational results were compared with experimental progression rates and temperatures measured for an example system composed of various Al/CuO-thermite mixtures with aluminum contents from 8% to 70%. The particle sizes were fixed to micrometer-scale. The curve of progression rate calculations depending on the aluminium particle concentration and their distribution show the same shape as the experimental results.