This paper is concerned with marginal analysis in the detailed estimation method. In a broad sense all estimates are marginal estimates in as much as they are concerned with creating changes from a current course of action. Only after a detailed ostinato is made can the engineering realize and exploit the advantages of marginal analysis. Marginal analysis is good tool for nonlinear break-even analysis adapted real world, and much more information and efficiency of CVP(Cost-Volumn-Profit) are provided with marginal analysis.