Work out your Schedule Performance Index in seconds. Enter earned value and planned value, and get your SPI, schedule variance, and a plain-English read on whether the project is ahead of or behind schedule.
Tip: planned value is what your baseline said should be done by today, in budget dollars.
The Schedule Performance Index (SPI) measures how efficiently a project is progressing against its baseline schedule, in budget dollars. It compares the work you've actually earned to the work you planned to have done by now. An SPI of 1.0 is exactly on schedule; 0.90 means you've completed only 90% of what the plan called for by this point.
Where EV (earned value) is the budgeted cost of the work actually completed, and PV (planned value) is the budgeted cost of the work your baseline scheduled to be complete by now.
| SPI | What it means |
|---|---|
| > 1.00 | Ahead of schedule |
| = 1.00 | Exactly on schedule |
| 0.95 – 1.00 | Slightly behind — watch it |
| < 0.95 | Behind schedule — needs schedule recovery or a re-forecast |
Worked example: you've earned $1.85M of budgeted work against a $2.0M plan. SPI = 1.85 / 2.0 = 0.93 — about 7% behind schedule, a schedule variance of −$150k.
SPI is measured in dollars, not time, and it always drifts back toward 1.0 as a project finishes — because by completion all planned value has been earned, even if you finish late. So a healthy SPI late in a project can hide a slipping finish date. Always pair SPI with the full earned-value picture and a critical-path check, not on its own.
SPI (Schedule Performance Index) is schedule efficiency: EV / PV. 1.0 is on schedule, above 1.0 is ahead, below 1.0 is behind.
Divide earned value by planned value: SPI = EV / PV. Earned $1.85M against a $2.0M plan gives SPI = 0.93.
1.0 or above is good. 0.95–1.0 is a mild slip to watch; below 0.95 needs action. Remember SPI trends to 1.0 near the end, so check the critical path too.
Aegis pairs SPI with real critical-path and Monte-Carlo forecasting from your P6 or MS Project schedule — so a healthy index can't hide a slipping finish date.
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