A robust computational framework based on the thermodynamic approach for determining monomer partitioning in monodisperse/polydisperse multi-component emulsion systems was introduced. The numerical methods were applied to determine monomer partitioning in three monodisperse and one hypothetical polydisperse multi-monomer emulsion systems. Larger particle size promotes the swelling ability of particles and increases the monomers content ratio for monomer with lower solubility in particle phase. For polydisperse systems, there is a strong particle size dependency of polymer volume fraction and the volumetric ratio of the monomers in particles, even for large particles and/or under partial swelling condition. In monodisperse systems, the particle size independency of monomers' volumetric ratio is only valid for large enough particles and/or partial swelling conditions. The results show that the prediction of the thermodynamic model can be brought close to reasonable results only with values of interfacial tensions, which are several times higher than the experimentally measured data.