This study evaluates the reactivity of acidic resins through mathematical modeling. To assess the reactivity of resins, a copolymerization model was used, making it possible to estimate chain sequences distribution along their polymeric matrices. A model for the reaction catalyzed by these resins, whose equations were based on power law and molar balances, was coupled to the copolymerization model to describe the whole process. Resin properties were collected from the literature and compared to data provided by the copolymerization model, resulting in a linear correlation between the weighted average chain densities measured by ISEC and the total concentration of sequences between cross-links (R 2 = 0.988). The prediction ability of the developed model was compared to a literature approach, which depends on an experimental characterization of the resins by Inverse Steric Exclusion Chromatography (ISEC). Akaike Information Criterion revealed that the models exhibit comparable predictive capabilities, demonstrating that the developed model is able to simulate reactions catalyzed by gel-type resins without requiring equipment for morphology characterization.