In an early design stage of LSI designing, finding out the proper parameters for power planning is important from the viewpoint of cost minimization. In this paper, we present simple analytical formulas which are used to obtain the initial parameters close to the proper power distribution networks in the early design stage. The formulas for estimating static and pseudo-dynamic voltage drops (IR-drops) are derived by the response surface method (RSM). By making the formulas once, they can be used for the general power planning for the power-grid style in any process technology.