In this paper, based on exponentially distributed trap density of states (DOS) for grain boundary, a solution to effective mobility (μ_eff) is derived. Within the model, an effective width of grain boundary (GB) depletion region (L_GB.eff) and drain induced grain barrier lowering effect on GB barrier height (ψ_B), is considered. The μ_eff model is then verified with μ_eff extracted from simulation. To this end, a computer aided design simulation is calibrated against the experimental data and μ_eff is then calculated from the simulated channel current. The μ_eff model is compared with calculated μ_eff to validate the model and a good agreement between them is achieved. In addition, we also investigate the dependence of μ_eff on GB DOS parameters and device temperature. The same validation process is also performed at various GB locations and angles to analyze the effect of GB shape on μ_eff.