Currently, finite element analysis (FEA) serves as the only analytical tool used in the evaluation of seals. The FEA does not allow the dynamic analysis of the seal, which must be performed experimentally. As a result, the designing of a seal can be a costly and extensive procedure. The aim of this project has been to develop a numerical model and computer program that will have the ability to predict key seal performance characteristics, such as leakage and friction. This numerical model provides a means for evaluating potential seal designs, which can be performed without having to endure the costs of creating and evaluating the performance of the seal. Thus, the numerical model reduces the time and cost involved in evaluating seal designs. The numerical model developed differs from previous models as the effects of mixed lubrication and surface roughness are investigated. This model consists of three coupled analyses of fluid mechanics, deformation, and contact mechanics. After computational procedure has converged coupling the three analyses, auxiliary calculations are performed to obtain the quantities of leakage rate and friction force. These obtained results then allow the evaluation of the seal design, which will lead to better seal designs with lower friction and less (or no) leakage. The results obtained for a typical hydraulic seal show that the leakage characteristics depend strongly on the seal roughness.