What Is Schedule Performance Index (SPI)? EDGEBIC Definition

Schedule Performance Index (SPI) is the ratio of earned value to planned value (EV divided by PV) that tells you whether a job is ahead of or behind its schedule. An SPI of 1.0 means the work earned so far exactly matches what the plan expected by now; below 1.0 the job is behind, above 1.0 it is ahead. SPI is a productivity-of-time measure: it says nothing about cost, which is what its partner index CPI covers.

This entry is part of the EDGEBIC by User Solutions glossary series; for the wider vocabulary of production planning, see the manufacturing glossary.

How SPI Works

Earned Value Management tracks three numbers for every job. Planned value (PV) is the hours that were scheduled to be done by the reporting cut-off. Earned value (EV) is how much of the plan's work has actually been completed, expressed in the same hours. Actual cost (AC) is the hours truly logged against the job. SPI compares the first two.

Because both EV and PV are measured in the same unit (planned hours), the ratio is dimensionless. SPI 0.75 does not mean "75 hours"; it means the job has banked three-quarters of the value it should have banked by this date. That framing lets a planner compare a 40-hour job and a 400-hour job on the same scale.

SPI drifts as the week progresses. A job that slips its early steps posts an SPI below 1.0; if it later catches up, the index climbs back toward 1.0. Reading the trend matters more than any single snapshot, which is why EDGEBIC keeps the report point-in-time and lets you re-run it against any cut-off date.

A Concrete Example

Consider job J-100, product Widget A, with five routing steps totaling 50 planned hours. The report is run halfway through step 4.

Budget at Completion (BAC) is 8 + 12 + 24 + 4 + 2 = 50 hours. Planned value clips each step to the cut-off: steps 1 through 3 fully past (44 hours) plus half of step 4 (2 hours), so PV = 46 hours. Actual hours logged total 55, which caps percent complete at 100, so earned value equals the full 50 hours.

SPI = EV divided by PV = 50 divided by 46 = 1.09.

The job is 9 percent ahead of schedule: the completed steps finished faster than the plan expected. That the same job is over budget (CPI 0.91) is a separate story, and the two indices sitting next to each other is precisely the point of Earned Value.

How EDGEBIC Computes and Shows SPI

SPI lives in the Earned Value (EVM) report, one of the eighteen built-in report panes. The report loads every scheduled job, computes BAC, PV, EV, AC, SPI, CPI, EAC, and VAC for each, and displays them in a single grid. Two behaviors are worth knowing:

• The grid sorts ascending by SPI, so the worst-performing jobs (lowest SPI, most behind) sit at the top where they need attention. A planner opening the report reads the trouble first.
• SPI defaults to 1.0 when PV is zero. For a job that has not started, there is nothing to compare, so the report avoids a divide-by-zero by showing 1.0. Treat that as "no data yet", not "perfect".

Every column on the pane carries a built-in definition. Click Column Details and the SPI row expands to show the formula (EV divided by PV), the unit (ratio), and worked examples, all served from the same self-explaining reports system that documents every report grid. The full pane catalog lives in the EDGEBIC reports guide, and if your real question is delivery dates rather than pace, the reports that answer "are we on time" walk through the on-time and late-job panes alongside EVM.

SPI pairs with cost efficiency through Cost Performance Index: read them together, never in isolation.