CPI is calculated by dividing BCWS / ACWP (budgeted cost for work scheduled/actual cost for work performed) and multiplying by 100 to express it as a percentage. A CPI of 100% means that the estimated cost was exactly right and the project came in exactly on budget. If it is under 100%, the work cost less effort than planned; a CPI greater than 100% means that the estimate was not adequate for the work involved. CPI can be used either to compare projects with each other or to compare phases within a project. For example, if the programming tasks took twice as long as estimated but every other type of task in the project took less time than estimated, the total variance for the project might still be low. However, the problem can still be pinpointed by calculating the CPI for each phase of development.