Earned Schedule

Definition

Earned Schedule (ES) is a project controls technique developed by Walt Lipke in the early 2000s that re-expresses schedule progress in time units rather than cost units. Classic Earned Value Management measures SV and SPI in dollars; that maths breaks down as a project approaches its planned finish, where SPI artificially trends to 1.0 even on late projects. ES fixes this by asking a different question: at what point in the past was the work I have actually completed planned to be done? The gap between that point and the data date is the schedule variance in time — SV(t) — and the ratio is SPI(t).

Why It Matters

I learned to trust ES the hard way. On a refinery turnaround, the EVM dashboard showed SPI = 0.98 three weeks from completion and the steering committee relaxed. Earned Schedule on the same data showed SPI(t) = 0.84 and a forecast finish six weeks late. The team that was paying attention to ES had already moved equipment and crews; the team relying on cost-based SPI was blindsided. That moment changed how I report schedule performance permanently.

The Maths, Briefly

Plot the PV (planned value) cumulative curve over time. For any data date, take the EV (earned value) achieved and project it horizontally onto the PV curve; read off the time at which that EV was planned to be earned. That time is ES. Then:

• SV(t) = ES − AT (Actual Time)
• SPI(t) = ES ÷ AT
• IEAC(t) = PD ÷ SPI(t) where PD is planned duration — a forecast finish in time units

The formulas are simple. The leverage they give a controls team is enormous.

Real-World Construction Example

On a $480M hospital project I supported, classic SPI sat between 0.95 and 1.02 for the last eight months despite obvious slippage on the curtain wall. ES(t) told the truth: by month 22 of a planned 30-month duration, ES was 19.4 months — meaning we'd earned only what was planned for month 19.4. SPI(t) = 0.88 and IEAC(t) projected a 34-month finish. We finished month 33. EVM said we were on time. ES told us a year out that we weren't.

Real-World IT Example

Earned Schedule applies to phased programmes, not sprints. On a 14-month core-banking migration, the steering committee tracked sprint velocity and a high-level EVM. SPI looked healthy. ES(t) computed against the migration's milestone-loaded baseline showed a steady erosion from 0.96 to 0.81 over six months. The slippage was hidden because deferred items kept rolling forward into "completed-but-not-yet-delivered" buckets. ES caught what burndown didn't.

Practical Lessons Learned

• ES only works with a credible baseline. Garbage PV in, garbage ES out.
• Pair ES with the critical path. ES is a summary metric; CPM tells you which activities are causing the drift.
• Use SPI(t) for forecasting, not for stakeholder pressure. Teams hide bad news from punitive metrics.
• Recompute monthly, not just at gate reviews. Trends matter more than snapshots.

Common Mistakes

• Confusing SPI and SPI(t). They mean different things; reporting both as "SPI" misleads everyone.
• Computing ES without a time-phased PV curve. A milestone list is not a PV curve.
• Treating IEAC(t) as a commitment date. It's a forecast based on present trends; if trends change, so does the forecast.
• Ignoring out-of-sequence progress. ES assumes work is being earned roughly in the planned order; large out-of-sequence work distorts the reading.
• Reporting only at the project level. ES at WBS-level 2 or 3 is where the diagnostic value lives.

Expert Tips

• Always show ES and CPM together. One is the temperature, the other is the diagnosis.
• Plot ES vs AT as a line chart over time. The slope tells you whether the project is gaining or losing ground.
• Calibrate against historical projects. Your organisation's SPI(t) at 60% complete is a far better predictor than industry averages.
• Brief executives in time, not dollars. "We are 2.8 months behind plan" lands harder than "SV is negative $4.2M".
• Use the CPI/SPI/EVM calculator on PMMilestone.org to cross-check manual computations before publishing.

Key Takeaways

• Earned Schedule converts schedule performance into time units, eliminating EVM's late-project blind spot.
• SPI(t) and IEAC(t) are honest forecasters; classic SPI is not, beyond about 60% complete.
• Pair ES with CPM and with WBS-level reporting for diagnostic power.
• It works on construction, capital projects, and phased IT programmes — anywhere you have a credible time-phased baseline.

Related Encyclopedia Entries

• Earned Value Management
• Cost Performance Index
• Estimate at Completion
• Critical Path Method
• S-Curve
• Baseline Schedule

Related Research Articles, Case Studies & Tools

• CPI/SPI/EVM Calculator
• Project Controls Academy
• Learning Tracks
• Books & Publications
• Earned Schedule research notes
• Hospital project ES case study