Schedule Variance (SV) Formula: SV = EV - PV Explained for Construction

Schedule Variance (SV) tells you whether your project is ahead or behind programme, but it measures the gap in pounds, not in time. That catches people out. SV is the difference between Earned Value (what you've completed) and Planned Value (what you should have completed by now). Positive means ahead. Negative means behind. Zero means you're exactly on programme, which, in my experience, happens for about one reporting period on any given project before reality kicks in.

SV = EV - PV

This term is part of the earned value definitions glossary. For the full variance breakdown including Cost Variance, see the cost and schedule variance page.

The Formula

Where:

• EV = Budgeted Cost of Work Performed. The value of work actually completed.
• PV = Budgeted Cost of Work Scheduled. The value of work that should be complete by now, per your baseline programme.

The result is always in currency units (pounds). SV = -£1.3M doesn't mean you're £1.3M over budget. It means you're behind schedule by a quantity of work that was budgeted at £1.3M. The distinction matters.

How SV Works Visually

 SCHEDULE VARIANCE – EV vs PV at Month 8 ============================================ £M | 10┤ ┌────────┐ | │ │ 9┤ │ │ | │ PV │ 8┤ ┌─────────┐ │ £8.4M │ | │ │ │ (should │ 7┤ │ EV │ │ have │ | │ £7.1M │ │ done) │ 6┤ │ (what │ │ │ | │ we did) │ │ │ 5┤ │ │ │ │ | │ │ │ │ 4┤ │ │ │ │ | │ │ │ │ 3┤ │ │ │ │ | │ │ │ │ 2┤ │ │ │ │ | │ │ │ │ 1┤ │ │ │ │ | │ │ │ │ 0┼─────────────────┴──────────┴───────┴────────────── EV PV SV = EV - PV = £7.1M - £8.4M = -£1.3M ──────────────────────── BEHIND PROGRAMME by £1.3M worth of work The gap between the bars = schedule variance PV is taller = we planned to be further ahead

That -£1.3M gap represents work that should be in the ground but isn't. On this project, it might be a delayed piling rig, a late design approval, or a compensation event that's disrupted the programme. SV tells you there's a problem. It doesn't tell you why.

The Convergence Problem, SV's Fatal Flaw

Here's the thing nobody tells you when they introduce SV. It lies to you at the end of the project.

As a project approaches completion, EV converges towards BAC (the total budget). PV also converges towards BAC. So SV converges towards zero, regardless of whether the project is on time. A project that finishes 6 months late will still show SV = 0 at completion, because all the planned work has eventually been done and all the budgeted work has been completed.

 SV CONVERGENCE PROBLEM ============================================= SV (£) | +1M ┤ ╱╲ Ahead | ╱ ╲ 0 ┤──╱──╱────╲───────────── ← SV always ends here | ╱ ╲ ╱ even if 6 months late! -1M ┤ ╲ ╱ | ╲ ╱ Behind -2M ┤ ╲___╱ | └────┬─────┬─────┬─────┬─────┬── Time 20% 40% 60% 80% 100% SV is MOST USEFUL in the first half (0-50% complete) SV is MISLEADING in the second half (50-100%) SV is USELESS at completion (always = 0) SOLUTION: Use SV(t) – schedule variance in time units See: earned schedule and SV(t)

This is why the Earned Schedule extension was developed. SV(t) measures schedule variance in time units, not cost units, and doesn't converge to zero. On any project past 60% complete, I'd recommend using SV(t) alongside SV. Before 60%, traditional SV is fine.

Worked Example: £20M Flood Defence at Month 8

Common Mistakes

1. Interpreting SV as a cost figure. SV = -£1.3M doesn't mean you're overspending by £1.3M. It means you're behind schedule by £1.3M worth of work. You might be perfectly on budget but just haven't got the work done yet. Cost performance is measured by CV, not SV.
2. Using SV alone past 60% complete. Once you're in the second half of the project, SV starts converging towards zero. A project that's badly behind will show an improving SV simply because EV is catching up to BAC. Supplement with SV(t) for an honest picture.
3. Ignoring the sign of SV. Positive SV isn't always good news. If EV is running ahead of PV because the team is front-loading easy work to make progress look healthy, the underlying critical path might still be behind. Check which activities are driving the positive variance.
4. Not decomposing SV to package level. A project-level SV of -£1.3M could be one package at -£2M and another at +£700K. The aggregate number masks opposite problems in different parts of the project. Always break SV down by control account.

Frequently Asked Questions

Why is schedule variance measured in pounds instead of time?

Because EV and PV are both measured in pounds. SV = EV - PV, and since both inputs are currency values, the output is too. It's a legitimate criticism of traditional EVM, measuring schedule performance in cost units isn't intuitive. That's exactly why Earned Schedule was developed. SV(t) gives you the same insight but in weeks or months, which is what planners and project managers actually care about.

What's a good SV threshold for triggering a recovery plan?

There's no universal answer, but most UK contractors I've worked with use SV% as the trigger. Anything beyond -10% gets a yellow flag (investigate). Beyond -20% gets a red flag (mandatory recovery plan within two weeks). The actual thresholds should be set during baseline approval and documented in the project controls procedures.

Does SV work on NEC4 Option A differently than Option C?

The formula is identical. The difference is in how PV is derived. On Option A, PV comes from the priced activity schedule mapped to the Accepted Programme. On Option C, PV comes from the Defined Cost allocation against the Accepted Programme. The maths is the same; the source data differs.

Can SV be positive even when the project is behind on the critical path?

Yes. Absolutely. This is one of the most dangerous misreadings in EVM. If non-critical activities are ahead of schedule but the critical path is behind, overall SV can be positive while the project is actually slipping on completion date. Always check SV against the critical path, not just the aggregate.