SPI Calculator
Calculate Schedule Performance Index (SPI) to evaluate whether your project is ahead, on, or behind schedule using Earned Value Management methodology.
SPI = EV / PVInterpretation Guide
- SPI > 1.0Project is ahead of schedule.
- SPI = 1.0Project is exactly on schedule.
- 0.9 ≤ SPI < 1.0Mild slip — investigate causes.
- SPI < 0.9Material delay — recovery plan required.
Example
If your project planned $100,000 of work this month (PV) but only delivered $80,000 worth of completed scope (EV), SPI = 0.80 — meaning you delivered 80% of what you planned.
Real-world use cases
- Weekly PMO status reporting
- Construction progress reviews
- Portfolio dashboards and executive summaries
- Forecasting completion dates with EAC and TCPI
Common mistakes
- Using actual cost (AC) instead of EV.
- Comparing SPI across projects of different sizes without context.
- Ignoring critical-path tasks while celebrating an overall good SPI.
Professional tips
- Pair SPI with float-erosion analysis for true schedule health.
- Track SPI trend over time — direction matters more than absolute value.
- Combine with CPI for an integrated performance view.
Frequently asked questions
What is a good SPI value?
Anything at or above 1.0 indicates the project is performing on or better than the schedule baseline.
Can SPI be misleading near project end?
Yes. Near completion, SPI naturally trends to 1.0 even on late projects. Use Earned Schedule (ES) for late-phase analysis.
How often should I calculate SPI?
Weekly for active execution; bi-weekly or monthly during stable phases.
What this tool does
Calculate Schedule Performance Index (SPI) to evaluate whether your project is ahead, on, or behind schedule using Earned Value Management methodology.
It applies the standard formula SPI = EV / PV so planners, schedulers and PMOs get a defensible number they can put in front of a steering committee.
Looking for the underlying terminology? Open the PM Glossary or the PM Cheat Sheet for quick references on EVM, scheduling and risk terms.
When to use it
- Weekly PMO status reporting
- Construction progress reviews
- Portfolio dashboards and executive summaries
- Forecasting completion dates with EAC and TCPI
Typical owners: project managers, planning engineers, project controls leads and PMO analysts running weekly or monthly performance reviews on EPC, infrastructure, IT and construction projects.
How to interpret the result
Treat the number as a signal, not a verdict. Read it together with the trend over the last 3–6 reporting periods, the critical-path status, and the risk register before you change the plan.
- Compare against the baseline, not against another project.
- Investigate the drivers behind the value before reporting it up.
- Pair it with at least one complementary KPI (cost, schedule, risk or quality).
Worked example
If your project planned $100,000 of work this month (PV) but only delivered $80,000 worth of completed scope (EV), SPI = 0.80 — meaning you delivered 80% of what you planned.
In a real project review, document the inputs, the resulting value, the interpretation, and the corrective action you committed to. That audit trail is what turns a calculator output into a controls decision.
In-depth guide: SPI Calculator
Schedule Performance Index (SPI) is one of the two core Earned Value Management ratios codified by PMI in the PMBOK Guide and by AACE International in TCM Framework section 9.2. It compares the dollar value of work actually completed (Earned Value) against the dollar value of work that should have been completed by the data date (Planned Value). The output is a unitless ratio centred on 1.0 — above means ahead, below means behind.
In day-to-day project controls work, SPI is rarely consumed alone. It sits inside a performance pack alongside CPI (cost efficiency), VAC (variance at completion), and the schedule's float profile. The reason is simple: SPI tells you the magnitude of the slip in budget terms, but it does not tell you whether the slip is on the critical path, whether it is recoverable, or whether it is driven by a single late vendor or by systemic resource shortage.
On EPC, infrastructure and large IT programmes, SPI is typically reported weekly by the project controls lead and rolled up monthly into the PMO scorecard. Most enterprise PM platforms — Primavera P6 with the Project Reporter add-on, Microsoft Project Server, Deltek Cobra and Oracle Unifier — compute SPI natively from the cost-loaded schedule, so the calculator on this page is most useful for spot-checks, RFP responses, training, and projects that do not have a fully cost-loaded baseline.
When to use it (and when not to)
Use SPI any time you need a single number to summarise schedule performance for a non-technical audience. It is the right KPI for steering-committee slides, monthly PMO reports, executive dashboards, and stage-gate reviews. The fact that it is unitless makes it easy to compare across periods on the same project.
Avoid SPI as the primary signal in two situations: (1) when the project is past ~80% completion, because SPI mathematically trends toward 1.0 even on late projects — switch to Earned Schedule SPI(t) in that phase; and (2) when the schedule is not cost-loaded or the WBS is not stable, because SPI requires a reliable PV curve to be meaningful.
Related KPIs to read alongside
Pair SPI with CPI (cost efficiency), SV (schedule variance in dollars), TCPI (required future performance), and SPI(t) from Earned Schedule for late-phase projects. For programmes with strong delay-claim exposure, also track float erosion and the count of activities with negative float as leading indicators of an SPI deterioration two to three periods ahead.
Worked example — substation construction package
A 132/33 kV substation construction package has a 12-month baseline with a cost-loaded schedule. At the end of month 6, the PV curve says $4.2M of work should be complete. The earned-value rules-of-credit (50/50 for milestones, % complete for installation) say $3.6M of work is actually complete.
SPI = 3.6 / 4.2 = 0.857. That is below the 0.9 warning threshold, so the project is reported amber at the next progress meeting. The PMO does not stop there — they pull the schedule and find that the delay is concentrated in two civil-works activities on the critical path (rebar delivery, foundation pour). Total float on that path has dropped from 12 to 2 days.
The corrective action package combines a 2-week rebar acceleration (paid by the supplier under the LD clause), a temporary second civil crew funded from the management reserve, and a re-sequencing of the substation building handover to run in parallel with switchgear installation. The recovery plan is baselined at SPI 0.95 by month 8 and SPI 1.0 by month 10. Each subsequent month, the actual SPI is compared against this recovery curve, not against 1.0.
Decision table
| Signal | What it means | Recommended action |
|---|---|---|
| SPI ≥ 1.00 | On or ahead of plan in budget terms. | Hold — verify the EV calculation is honest, not optimistic claiming. |
| 0.95 ≤ SPI < 1.00 | Minor slip, within normal noise. | Note in PMO log, watch trend over next 2 periods. |
| 0.90 ≤ SPI < 0.95 | Material slip — investigate drivers. | Root-cause analysis on the bottom-quartile WBS elements. |
| SPI < 0.90 | Significant delay against baseline. | Formal recovery plan, escalate to sponsor, consider rebaseline. |
Common pitfalls in the field
- Mis-classifying EV is the single biggest source of bad SPI numbers. Teams under reporting pressure tend to claim earned value on work that is started but not yet measurable — pipework that is welded but not pressure-tested, code that is committed but not merged, civil works that are 'almost done'. Lock the rules of credit at baseline and audit them quarterly.
- Treating SPI as a target instead of a signal leads to gaming. If a contractor is paid against SPI ≥ 0.95, they will find a way to report 0.95 every period regardless of physical progress. The fix is to separate earning rules (objective, milestone-based) from reporting rules.
- Reading SPI without the schedule. A project can have SPI = 1.05 (ahead in dollars) and still miss its end date by months, because the work that was accelerated was non-critical and the critical path slipped. Always read SPI together with critical-path total float and the longest-path report.
Featured in Academy articles
This calculator is referenced in the FAQs of these Academy articles — read them to understand the theory behind the numbers.
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