S-Curve for Earned Value Management

Visualise EVM metrics with S-Curves: Planned Value, Earned Value, and Actual Cost plotted for schedule and cost variance analysis.

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Background

Earned Value Management (EVM) is the gold standard for project performance measurement. The S-Curve is its visual backbone — three curves plotted together: Planned Value (PV, the budget baseline), Earned Value (EV, work performed), and Actual Cost (AC, money spent). The gaps between these curves reveal schedule and cost variance at a glance.

The Three EVM Curves

PV (Planned Value): the baseline S-Curve showing cumulative budgeted cost of work scheduled. EV (Earned Value): cumulative budgeted cost of work actually performed. AC (Actual Cost): cumulative actual expenditure. When EV < PV, you're behind schedule. When AC > EV, you're over budget.

Key EVM Metrics from S-Curves

Schedule Variance (SV = EV − PV): gap between EV and PV curves. Cost Variance (CV = EV − AC): gap between EV and AC curves. Schedule Performance Index (SPI = EV/PV): ratio of EV to PV. Cost Performance Index (CPI = EV/AC): ratio of EV to AC. Values < 1.0 indicate problems.

How to Use This Calculator

Our S-Curve Calculator can be configured for earned value management projects. Follow these steps:

Define earned value management phases
Break the project into major phases with duration and resource/budget allocation.
Enter phase data
Each phase: name, duration, percentage of total effort or budget.
Generate baseline S-Curve
Calculator distributes effort and creates the planned progress curve.
Track actual progress
Update with actual cumulative data at regular intervals.
Compare and forecast
Overlay actual on baseline. Extrapolate for completion estimates.
Adjust resources
Use the forecast to reallocate resources and correct variances.

Applications

S-Curves support several critical functions in this domain:

Project Health Dashboard

Three curves on one chart give instant project health. All three converging = on track. EV below PV = behind schedule. AC above EV = over budget. Non-project managers can read this without training.

Forecasting at Completion

EAC = BAC / CPI (assuming current cost efficiency continues). If CPI = 0.85 on a $10M project, EAC = $11.76M. The S-Curve extension shows when you'll hit the new budget.

Portfolio-Level EVM

Aggregate PV, EV, and AC across all projects for portfolio-level performance. A single set of curves shows whether the entire portfolio is on track.

Frequently Asked Questions

What is Planned Value (PV)?

The cumulative budgeted cost of work scheduled. It's the baseline S-Curve, set before the project begins. At any point, PV tells you how much work should have been completed by that date.

What is Earned Value (EV)?

The cumulative budgeted cost of work actually performed. If you planned to complete $500K of work and actually completed $400K, EV = $400K. EV is the objective measure of progress.

What is Schedule Performance Index (SPI)?

SPI = EV / PV. If SPI = 0.85, you've completed 85% of the work you planned. An SPI < 1.0 means behind schedule; > 1.0 means ahead. SPI is more useful than SV because it's a ratio (comparable across projects).

How do you forecast final cost with EVM?

Estimate at Completion (EAC) = Budget at Completion (BAC) / CPI. If BAC = $10M and CPI = 0.90, EAC = $11.11M. This assumes the cost efficiency trend continues. For a more optimistic forecast, use EAC = AC + (BAC − EV).