Winkler method is widely used in computer analysis of raft foundations due to its simplicity. In this method, soil is represented as medium consisting of infinite number of elastic, identical, but independent springs. The stiffness of the springs is the coefficient of subgrade reaction, ks. The inadequacy of this modeling to account for the elastic continuity of soil is its serious limitation. The computation of ks is very difficult as it depends on several factors like stiffness of raft and superstructure, soil properties and depth of embedment of foundation. Hence the accuracy of analysis of raft foundation depends on the estimate of representative ks considering the above factors. The present study was carried out to investigate the impact of changing coefficient of subgrade reaction values in the design of raft foundation. General trends were established for the variation of bending moment, shear and settlement of raft with change in values of ks. The Winkler method is then compared with continuum modeling of soil. Finally two rafts were designed varying ks values and its impact on structural design and cost of execution is presented. © Research India Publications.