This paper focus on the effect of volute tongue clearance variation on the performance of backward-curved blades centrifugal blower. The four types of casings of the centrifugal blower with different volute tongue clearances of 6%, 8%, 10% and 12.5% of impeller diameter were used for numerical and experimental analysis. Computational fluid dynamics model was developed for for the numerical analysis based on experimental setup. Reynolds-averaged Navier-Stokes equations with the standard k-ε turbulence model were discretized with finite volume approximations. The Numerical results were validated with the experimental results by using IS: 4894-1987. The performance parameters such as total pressure, efficiency and flow rate of the blower were calculated. The results show that the volute tongue clearance has a significant effect on the performance of centrifugal blower and these parameters increases with decrease in volute tongue clearances.