To design a safe substation grounding grid, it is necessary to compute the split factor for earth fault current and also current distribution in other possible paths. In this paper, a novel, simple and accurate method is developed for determination of this factor. In the proposed algorithm grounding grid impedance of adjacent substations, dissimilar tower footing resistances, different parallel circuits, more than one earth wires and different spans in transmission lines can be considered. In addition, the formulation for the earth faults through line towers is presented. Finally, the results are compared with the addressed cases that are comparable and show good agreement and accuracy.