Cost Performance Index (CPI) is a numerical value that helps you to understand whether the work related to the model item is within, over or on budget. It helps to evaluate the financial efficiency of a project or cost item.To calculate CPI of a cost item, you can divide the budgeted cost of work completed or earned value (EV), by the actual cost (AC) of the work performed.
CPI = EV/AC
CPI values of each cost item is displayed in the cost grid.