Schedule Variance Percentage (SV%) in EVM Explained

<div class="ge-article-wrapper"><nav class="ge-toc" aria-label="Table of contents"><p class="ge-toc-label">In this article</p><ul class="ge-toc-list"><li><a href="#the-formula">The Formula</a></li><li><a href="#why-sv-matters-the-normalisation-problem">Why SV% Matters: The Normalisation Problem</a></li><li><a href="#the-relationship-between-sv-sv-and-spi">The Relationship Between SV%, SV, and SPI</a></li><li><a href="#worked-example-comparing-two-projects-in-a-programme">Worked Example: Comparing Two Projects in a Programme</a></li><li><a href="#common-mistakes">Common Mistakes</a></li><li><a href="#frequently-asked-questions">Frequently Asked Questions</a></li></ul></nav><article class="ge-article-body"><p>Schedule Variance Percentage (SV%) normalises <a href="/en/earned-value/definitions/schedule-variance">Schedule Variance</a> so you can compare programme performance across projects of different sizes. Raw SV is measured in pounds, which makes cross-project comparison meaningless. A -£500K SV on a £5M project is a crisis. The same -£500K on a £50M project is a rounding error. SV% strips out the scale and tells you how far behind (or ahead) you are as a percentage of the plan.</p><p><strong>SV% = (SV / PV) x 100</strong></p><p>Or equivalently: <strong>SV% = ((EV - PV) / PV) x 100</strong></p><p>This term is part of the <a href="/en/earned-value/definitions">earned value definitions glossary</a>. For the raw pound-value metric, see <a href="/en/earned-value/definitions/schedule-variance">Schedule Variance (SV)</a>.</p><h2 id="the-formula">The Formula</h2><div class="ge-formula-box ge-anim"><span class="ge-formula-label">Formula</span><code>SV% = SV / PV x 100</code></div><p>Where:</p><ul><li><strong>SV</strong> = <a href="/en/earned-value/definitions/earned-value">Earned Value</a> minus <a href="/en/earned-value/definitions/planned-value">Planned Value</a></li><li><strong>PV</strong> = cumulative budgeted cost of work scheduled to date</li></ul><div class="ge-table-wrap ge-anim"><table class="ge-table"><thead><tr><th>SV% Range</th><th>Status</th><th>Typical Response</th></tr></thead><tbody><tr><td>> +10%</td><td>Well ahead</td><td>Verify it's genuine progress, not front-loading</td></tr><tr><td>+5% to +10%</td><td>Ahead</td><td>Monitor. Ensure quality isn't being sacrificed for speed</td></tr><tr><td>-5% to +5%</td><td>On track</td><td>Normal variance band on most construction projects</td></tr><tr><td>-10% to -5%</td><td>Slipping</td><td>Investigate root cause. Yellow flag</td></tr><tr><td>< -10%</td><td>Serious delay</td><td>Mandatory recovery plan. Red flag</td></tr></tbody></table></div><p>These thresholds aren't gospel. I've worked on projects where -5% was acceptable (complex M&amp;E with long procurement lead times) and others where -3% triggered an escalation (time-critical rail possessions with fixed handback dates). Set your thresholds during <a href="/en/earned-value/definitions/performance-measurement-baseline">baseline</a> approval and stick to them.</p><h2 id="why-sv-matters-the-normalisation-problem">Why SV% Matters: The Normalisation Problem</h2><p>Here's the scenario that makes SV% essential.</p><pre class="ge-ascii-diagram ge-anim"> WHY RAW SV IS MISLEADING ACROSS PROJECTS ============================================= PROJECT ALPHA (£5M retail fit-out) ├── PV at month 4 = £2,000,000 ├── EV at month 4 = £1,500,000 ├── SV = -£500,000 └── SV% = -£500K / £2M = -25% ← CRISIS. Quarter of planned work not done. PROJECT BETA (£50M hospital) ├── PV at month 10 = £22,000,000 ├── EV at month 10 = £21,500,000 ├── SV = -£500,000 └── SV% = -£500K / £22M = -2.3% ← Minor blip. Easily recoverable. ────────────────────────────────────────────────── SAME SV (-£500K) COMPLETELY DIFFERENT SEVERITY ────────────────────────────────────────────────── Without SV%, a portfolio director looking at two SV figures of -£500K might treat both projects equally. With SV%, it's obvious: Alpha is in serious trouble, Beta is fine.</pre><p>On a programme with 8 or 10 live projects, the portfolio director doesn't have time to mentally adjust every SV figure for project size. SV% does that automatically. It's the metric that belongs in the programme-level dashboard.</p><h2 id="the-relationship-between-sv-sv-and-spi">The Relationship Between SV%, SV, and SPI</h2><p>These three metrics all measure the same thing, schedule performance, but from different angles:</p><pre class="ge-ascii-diagram ge-anim"> THREE WAYS TO SAY "WE'RE BEHIND SCHEDULE" ============================================= SV = EV - PV = -£1,300,000 (how much behind, in pounds) SV% = SV / PV x 100 = -15.5% (how much behind, as a proportion of plan) SPI = EV / PV = 0.845 (efficiency: £0.85 of progress per £1 planned) ────────────────────────────────────────────────── MATHEMATICAL RELATIONSHIP: SV% = (SPI - 1) x 100 ────────────────────────────────────────────────── So SPI = 0.845 → SV% = (0.845 - 1) x 100 = -15.5% Use SV for absolute impact ("we're £1.3M behind") Use SV% for cross-project comparison ("Project A is -15%, B is -3%") Use SPI for efficiency and forecasting ("at this rate.")</pre><p>The mathematical link between SV% and <a href="/en/earned-value/definitions/schedule-performance-index">SPI</a> is straightforward: SV% = (SPI - 1) x 100. An SPI of 0.90 always gives SV% = -10%. They're two expressions of the same ratio.</p><h2 id="worked-example-comparing-two-projects-in-a-programme">Worked Example: Comparing Two Projects in a Programme</h2><span class="ge-worked-label">Worked Example</span><div class="ge-callout ge-anim"><p><strong>Scenario:</strong> A Tier 1 contractor runs two NEC4 Option C projects simultaneously. The commercial director reviews both at the monthly programme board (October 2025).</p><p><strong>Project 1: £5M Retail Fit-out in Manchester</strong></p><ul><li><a href="/en/earned-value/definitions/budget-at-completion">BAC</a> = £5,000,000</li><li>Duration: 8 months</li><li>Current month: 4 of 8 (50% through programme)</li><li>PV = £2,000,000</li><li>EV = £1,500,000</li><li>SV = £1,500,000 - £2,000,000 = <strong>-£500,000</strong></li><li>SV% = -£500,000 / £2,000,000 x 100 = <strong>-25.0%</strong></li><li>SPI = 0.750</li></ul><p><strong>Project 2: £50M Hospital Extension in Birmingham</strong></p><ul><li>BAC = £50,000,000</li><li>Duration: 24 months</li><li>Current month: 10 of 24 (42% through programme)</li><li>PV = £22,000,000</li><li>EV = £21,500,000</li><li>SV = £21,500,000 - £22,000,000 = <strong>-£500,000</strong></li><li>SV% = -£500,000 / £22,000,000 x 100 = <strong>-2.3%</strong></li><li>SPI = 0.977</li></ul><p><strong>The dashboard without SV%:</strong></p><div class="ge-table-wrap ge-anim"><table class="ge-table"><thead><tr><th>Project</th><th>SV</th></tr></thead><tbody><tr><td>Retail fit-out</td><td>-£500,000</td></tr><tr><td>Hospital extension</td><td>-£500,000</td></tr></tbody></table></div><p>Looks equal. Feels like both need the same intervention.</p><p><strong>The dashboard with SV%:</strong></p><div class="ge-table-wrap ge-anim"><table class="ge-table"><thead><tr><th>Project</th><th>SV</th><th>SV%</th><th>SPI</th><th>Status</th></tr></thead><tbody><tr><td>Retail fit-out</td><td>-£500,000</td><td>-25.0%</td><td>0.750</td><td>RED. Recovery plan needed immediately</td></tr><tr><td>Hospital extension</td><td>-£500,000</td><td>-2.3%</td><td>0.977</td><td>GREEN. Normal variance, monitor</td></tr></tbody></table></div><p>Now the commercial director knows exactly where to focus. The retail fit-out at -25% needs a recovery plan by Friday. The hospital extension at -2.3% just needs monitoring.</p></div><h2 id="common-mistakes">Common Mistakes</h2><ol><li><strong>Using SV instead of SV% for portfolio reporting.</strong> If you're comparing multiple projects, raw SV is misleading. A £60M project will almost always have a larger SV than a £3M project. SV% lets you compare apples to apples.</li><li><strong>Setting the same SV% threshold for all project types.</strong> A -10% threshold makes sense for a straightforward civils job. On a complex M&amp;E-heavy project with long procurement chains, -10% might be structurally normal for the first three months while equipment is on order. Tailor thresholds to the project type.</li><li><strong>Forgetting the convergence problem.</strong> SV% inherits the same convergence-to-zero flaw as SV. As the project nears completion, both EV and PV approach <a href="/en/earned-value/definitions/budget-at-completion">BAC</a>, so SV shrinks and SV% trends towards zero. In the last 20% of a project, SV% becomes unreliable. Use time-based metrics like <a href="/en/earned-value/definitions/schedule-variance-time">SV(t)</a> instead.</li><li><strong>Dividing by zero at the start.</strong> At month 0, PV = 0. SV% = SV / 0 is undefined. Most EVM systems handle this by returning null until the first reporting period where PV > 0. Don't manually force it to zero. That implies on-track performance when you have no data.</li></ol><div class="ge-product-note ge-anim"><p><strong>How Gather helps.</strong> Gather's AI reads your site diaries daily and maps progress against your cost-loaded programme, giving you accurate earned value data without manual spreadsheet updates. <a href="https://gatherinsights.com/contact">Book a demo</a> to see it working on a live NEC4 project.</p></div><h2 id="frequently-asked-questions">Frequently Asked Questions</h2><h3>What SV% is considered acceptable on UK construction projects?</h3><p>Most Tier 1 contractors I've worked with use a traffic light system: green at -5% to +5%, amber at -10% to -5%, red below -10%. But these aren't industry standards, they're project-specific thresholds set during baseline approval. On a fast-track programme with tight possession windows, even -5% might trigger escalation. On a long-duration infrastructure scheme, -8% in the early months might be acceptable if the critical path has float.</p><h3>How often should SV% be calculated?</h3><p>Monthly, aligned with your <a href="/en/earned-value">earned value</a> reporting cycle. Some projects calculate it fortnightly, particularly on shorter-duration contracts (under 6 months) where a monthly snapshot doesn't give enough granularity. Weekly is usually overkill unless you're in a recovery phase and need to track whether acceleration measures are working.</p><h3>Does SV% suffer from the same convergence problem as SV?</h3><p>Yes. SV% = SV / PV, and since SV converges to zero at completion, SV% does too. A project that finishes 4 months late will show SV% = 0 at completion. For the second half of any project, supplement SV% with <a href="/en/earned-value/definitions/schedule-performance-index-time">SPI(t)</a> or <a href="/en/earned-value/definitions/schedule-variance-time">SV(t)</a> for an honest picture of schedule performance.</p></article></div>