Main factors in Electro Discharge Machining (EDM) are material removal rate and the relative electrode-tool wear. Material removal rate and the relative electrode-tool wear depends on many parameters in particular parameter of electrical discharge and properties of electrode materials. The developed mathematical model describes relationship between parameters of material removal from electrodes and machining parameters. To estimate the volume of material removed from electrode, mathematical model of erosion for single electrical discharge has been applied. Estimation of material removal has been worked out using energy balance. The experimental results confirm the validity of the developed mathematical model.