A method and system is provided for estimating size and effort of software assurance project for distributing the estimated effort across the software assurance project phases. Particularly, the invention provides a method and system for estimating the software assurance project size based on the predefined weight ratios assigned to the test cases after classifying them into simple, medium and complex categories. Further, the invention provides a method and system for utilizing the estimated software assurance project size and organizational baseline productivity information for estimating the software assurance efforts. Further, the invention provides a method and system for distributing the estimated effort across the software assurance project phases.