Schedule Performance Index (SPI)
Schedule Performance Index (SPI) is an EVM efficiency metric that measures schedule performance as the ratio of earned value to planned value: SPI = EV / PV.
Explanation
The Schedule Performance Index measures how efficiently the project team is using its time. An SPI of 1.0 means the project is exactly on schedule. An SPI greater than 1.0 means the project is ahead of schedule, and an SPI less than 1.0 means the project is behind schedule.
The formula is SPI = EV / PV. For example, if EV = $40,000 and PV = $50,000, then SPI = 0.80, meaning the project is only accomplishing 80% of the planned work per unit of time. The project is progressing at 80% of its planned rate.
Like SV, SPI converges to 1.0 at project completion because all planned value will have been earned. SPI is used throughout the project to track schedule trends and is also used in some EAC formulas to forecast final project costs when schedule performance affects cost outcomes.
Key Points
- •Formula: SPI = EV / PV
- •SPI > 1.0 = ahead of schedule; SPI < 1.0 = behind schedule
- •Converges to 1.0 at project completion
- •Used in some EAC forecasting formulas
Exam Tip
SPI = EV / PV. Greater than 1.0 is good. An SPI of 0.8 means you are accomplishing only 80 cents of work for every dollar of planned work at this point.
Frequently Asked Questions
Related Topics
Planned Value (PV)
Planned Value (PV) is the authorized budget assigned to scheduled work, representing the value of work planned to be completed by a given point in time.
Earned Value (EV)
Earned Value (EV) is the measure of work performed expressed in terms of the budget authorized for that work.
Schedule Variance (SV)
Schedule Variance (SV) is an EVM metric that measures schedule performance as the difference between earned value and planned value: SV = EV - PV.
Cost Performance Index (CPI)
Cost Performance Index (CPI) is an EVM efficiency metric that measures cost performance as the ratio of earned value to actual cost: CPI = EV / AC.
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