A semiempirical expression is proposed to describe the dependence of the oscillatory surface force on both film thickness and particle volume fraction for a hard sphere fluid between hard walls. The expression is tested successfully against the predictions of integral equations, computer simulations and experimental data for liquid films containing ionic and nonionic surfactant micelles. The proposed expression can be used to interpret experimental data for stability of liquid films and colloidal dispersions, or can be incorporated in complex theoretical models of dynamics of liquid film drainage, or kinetics of flocculation in emulsions and suspensions.