This paper for use deals with the analysis of time periods of overhead water ware in the earthquake resistant design. An interactive softanalysisINTZE has been developed in FORTRAN 77 to carry out complete and design of water tanks on an IBM PC/XT. The code does tank. not give any expression for computing the lateral stiffness of the a tank Different to authors use different empirical expressions assuming expressions be equivalent cantilever beam. It is observed that these is proposed do not give satisfactory results. In this paper, an equation the results to determine the lateral stiffness of the tanks based on of dynamic analysis and theory of curve fitting.