For machine components like gears and bearings, working life calculation is one of the complex issues to deal with. This is because the mechanics of their operation is dependent on many parameters, like loading, friction and lubrication etc. Also the influence of these parameters on the component failure modes cannot be perfectly idealized. But in this regard, standards like AGMA (American Gear Manufacturers Association); ISO (International Standard Organization) and BS (British Standards) are quite useful on the basis of which theoretical working life for machine components under a specific failure mode can be predicted. In this paper with linear pitting failure mode assumptions, theoretical working life calculation has been made for a helical gear. BS-ISO 6336-2 standard is used for the gear theoretical life calculations. Furthermore, a wear debris analysis based experiment has been performed for the validation of theoretical calculation. A back to back gear testing rig has been used for the experimental validation. The experimental results show that the theoretical life calculation made on the basis of BS-ISO 6336-2 standards is fairly accurate.