calculation for earned cost index
1 CPI is computed by Earned Value / Actual Cost. 2  A value of above 1 means that the project is doing well against the budget. 3  Schedule Performance Index (SPI) : Represents how close actual work is being completed compared to the schedule. 4  SPI is computed by Earned Value / Planned Value. Cost Performance Index (CPI) : Represents the amount of work being completed on a project for every unit of cost spent. 2  CPI is computed by Earned Value / Actual Cost. 3  A value of above 1 means that the project is doing well against the budget.