This article presents a numerical methodology for estimation of flow field and pressure drop within a pleated air filter system that is typically used for automotive engine intake application. The flow field within the air filter housing was found to be highly non-uniform. This flow field was utilized to simulate the pressure drop across a typical pleated air filter element. Both the flow field and pressure drop were experimentally determined and they were found to be in good agreement with the simulation results. A set of new equations for pleat angle and maximum possible pleat radius was proposed to parameterize the pleat geometry. An optimal pleat pitch was determined to obtain minimum pressure drop and this was found to be dependent on pleat height significantly. The effect of pleat radius on the pressure drop was examined at optimum pleat pitch and pleat height. The pleat geometry and inlet velocity were found to be the key determinants of evolution of flow velocity within the pleated filter element and also at the vicinity of the filter media.