The kinetic model of free-radical surface graft polymerization developed is based on a conservational polymerization and molecular-weight distribution (CPMWD) numerical algorithm. The CPMWD model uses an implicit numerical technique to solve for the coupled monomer, surface site, and total growing polymer differential rate equations, which ensure that conservation of mass is maintained. The model formulation allows for the incorporation of kinetic rate coefficients, which are a function of the chain length of the reacting species, the solution viscosity, and the concentration of surface grafted polymer. The model also makes it possible to evaluate the monomer conversion, the graft yield and the molecular weight distributions of the homopolymer and surface-grafted polymer for the complete duration of the graft polymerization reaction. Its application was demonstrated for a model system of vinylpyrrolidone graft polymerization onto the surface of a silica substrate.