In this study, the power of the starting motors is defined as a function of engine volume. The study was started, by firstly examining the types of starting motors and determining of catalog values by describing the vehicles in which the starting motors are used. These values are compared with starting motor powers and friction powers which are implied by empirical and theoretical equations. In literature, calculation of the starting motor power is done by substituting the torque value found from the equations T= V-h.C-b.g, T = C(1)e(-C2n) into P-mm= T.omega. In these equations the revolution value is necessary to calculate the starting motor power with respect to engine volume. Different from the equations above, in this study, the revolution and constants in power term were assumed in new constants and starting motor power is calculated as a function of only the engine volume and described as P-mm= alpha . e (beta(Vh).) As a result, the ampiric equation in literature and the starting motor power, calculated from the equation found in this study, are compared with catalog values of starting motor powers. Comparison results show that ampiric equation results in literature give error about 40-70% and the values, obtained in this study give error 3.77% with respect to catalog values. This equation can be used in determination of power of the starting motor of integrated starter-alternator systems and power of starting system of hybrid vehicles, thus, more reliable and correct results can be reached.