Software failures are common and persistent and so are the dealing strategies. But the ultimate race is to be won by the best. Software failures are not only caused by the poor development effort but also by the poor requirement gathering and cost estimation. During the development lifecycle when the requirement are to be re-established or the cost and schedule of project are immediately threatened. The cost to develop the project with revisions remains an open question and calculated by intuition. This paper describes the possible cost of changing the software modules by considering the software development life cycle in its generic terms. An equation is presented in this paper that calculates the cost of revision based on the initial cost and the number of the phases to be revised. © 2013 International Information Institute.