Gears are one of the most critical components in mechanical power transmission systems. For reducing the noise level and power transmissions, the helical gears are used. The bending and surface strength of the gear tooth are considered to be one of the main parameters for the failure of the gears. For optimal design of gears and to reduce their failures, the area of research on stresses is becoming increasingly important. For determining the bending stresses, various three- dimensional solid models of gears of different specifications such as number of teeth, module and helix angle are generated by a powerful and modern solid modeling software and the final numerical solution would be done using ANSYS, which is a finite element analysis software package. All the analytical investigations would be carried out on the basis of Lewis stress formula.