Schedule Performance Index (SPI) is a measure of schedule efficiency expressed as the ratio of earned value to planned value.
It quantifies how efficiently the project is progressing compared to the schedule baseline and is a key metric in earned value management.
Key Characteristics
- Performance Ratio – Compares progress achieved (EV) to progress planned (PV)
- Indicator of Schedule Health – SPI = 1.0 means on schedule; < 1.0 is behind; > 1.0 is ahead
- Time-Focused – Measures schedule effectiveness, not duration or cost
- Used with EVM Metrics – Often paired with CPI for broader performance analysis
Example Scenarios
- An SPI of 0.80 indicates only 80% of planned work has been completed
- An SPI greater than 1.0 shows faster progress than expected
- Used in trend analysis to forecast project completion timing
Formula
Where:
- EV = Earned Value
- PV = Planned Value
Role in Project Monitoring and Control
- Supports Forecasting – Informs schedule-based estimates at completion
- Triggers Corrective Action – Helps identify when schedule recovery is needed
- Enhances Communication – Provides objective performance insight to stakeholders
- Feeds Into Trend Analysis – Tracks performance across reporting periods
See also: Cost Performance Index (CPI), Earned Value (EV), Planned Value (PV), Estimate at Completion (EAC), Schedule Forecasts.