This paper focusses on the designing and optimizing of a planetary gearbox for an FSAE formula electric car. The conventional arrangement of single or double stage reduction transmissions are bulky and uneconomical for an FSAE car because of their less power to weight ratios and high volume to weight ratios. A planetary gearbox gives a balance between weight and power transmitted. The procedure for the design was an iterative process to determine the optimum dimensions and materials for the gearbox. The method utilized the standard equations for gear calculations and computational simulations for designing and CAD modelling for various parts of the gearbox. The transmission shafts and bearings are designed using the standard force equations. The lubrication system is also selected according to established methods.