TCPI Formula: To-Complete Performance Index 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="#what-tcpi-actually-tells-you">What TCPI Actually Tells You</a></li><li><a href="#why-tcpi-matters-in-progress-meetings">Why TCPI Matters in Progress Meetings</a></li><li><a href="#worked-example-32m-station-upgrade">Worked Example: £32M Station Upgrade</a></li><li><a href="#tcpi-against-eac-the-alternative-denominator">TCPI Against EAC (The Alternative Denominator)</a></li><li><a href="#frequently-asked-questions">Frequently Asked Questions</a></li></ul></nav><article class="ge-article-body"><p>The To-Complete Performance Index (TCPI) is the reality check nobody wants to hear. It answers one question: "How efficiently do we need to perform from this point forward to hit our budget target?" If TCPI says you need to deliver £1.35 of value for every £1 spent when you've been averaging £0.87. That budget target is dead. You just haven't admitted it yet.</p><p>TCPI is part of the <a href="/en/earned-value/definitions">earned value definitions glossary</a>. For complete worked examples alongside EAC and ETC, see the <a href="/en/earned-value/eac-etc-tcpi">EAC, ETC and TCPI page</a>.</p><h2 id="the-formula">The Formula</h2><div class="ge-formula-box ge-anim"><span class="ge-formula-label">Formula</span><code>TCPI = (BAC - EV) / (BAC - AC)</code></div><p>Where:</p><ul><li><strong><a href="/en/earned-value/definitions/budget-at-completion">BAC</a></strong> = total approved budget</li><li><strong><a href="/en/earned-value/definitions/earned-value">EV</a></strong> = budgeted cost of work completed</li><li><strong><a href="/en/earned-value/definitions/actual-cost">AC</a></strong> = actual cost to date</li></ul><p>In plain English: the remaining work value divided by the remaining budget. If there's more work left than money, TCPI is above 1.0, meaning you need to outperform your current efficiency to hit the target.</p><h2 id="what-tcpi-actually-tells-you">What TCPI Actually Tells You</h2><p>TCPI translates a cost overrun into a required performance improvement. That's what makes it powerful. Instead of saying "we're £800K over budget," TCPI says "you need to deliver £1.12 of value per pound for the rest of the project to break even." Decision-makers understand the second statement instantly.</p><div class="ge-table-wrap ge-anim"><table class="ge-table"><thead><tr><th>TCPI Value</th><th>What It Means</th><th>Realistic?</th></tr></thead><tbody><tr><td><strong>< 0.90</strong></td><td>You can underperform and still hit budget</td><td>Comfortable position. Rare.</td></tr><tr><td><strong>0.90 to 1.00</strong></td><td>Perform at or slightly below budget rate</td><td>Achievable with current team.</td></tr><tr><td><strong>1.00 to 1.10</strong></td><td>Modest improvement needed</td><td>Achievable with focused management.</td></tr><tr><td><strong>1.10 to 1.20</strong></td><td>Significant improvement needed</td><td>Difficult. Requires changes to methods or resources.</td></tr><tr><td><strong>> 1.20</strong></td><td>Step change in performance required</td><td>Almost certainly unachievable. Re-baseline or present revised <a href="/en/earned-value/definitions/estimate-at-completion">EAC</a>.</td></tr></tbody></table></div><p>Here's the uncomfortable truth. If your <a href="/en/earned-value/definitions/cost-performance-index">CPI</a> has been sitting at 0.88 for four months and TCPI is 1.18, you're not going to improve performance by 34% for the remainder of the project. The gap between CPI and TCPI tells you how much reality has diverged from the plan.</p><h2 id="why-tcpi-matters-in-progress-meetings">Why TCPI Matters in Progress Meetings</h2><p>I've watched project managers spend 20 minutes explaining why CPI will recover to 1.0, "we've got efficiencies coming in the next phase, the subcontractor is remobilising with a better team, the design issues are resolved." Maybe. But what does the data say?</p><p>TCPI cuts through the optimism. It converts the recovery plan into a number. If recovery requires a TCPI of 1.25 when your historical CPI is 0.87, the burden of proof shifts to the person claiming recovery is achievable. They need to explain, specifically, how performance will improve by 44%. Not in general terms, in specifics.</p><p>That's why TCPI is the metric that ends arguments. Not because it's the most sophisticated formula in <a href="/en/earned-value">earned value management</a>. Because it's the most honest.</p><h2 id="worked-example-32m-station-upgrade">Worked Example: £32M Station Upgrade</h2><span class="ge-worked-label">Worked Example</span><div class="ge-callout ge-anim"><p><strong>Scenario:</strong> A £32M NEC4 Option C station upgrade programme. At month 12, the numbers are:</p><p><strong>BAC</strong> = £32M <strong>EV</strong> = £14.4M (45% complete) <strong>AC</strong> = £16.96M <strong>CPI</strong> = 0.849</p><p><strong>TCPI</strong> = (£32M - £14.4M) / (£32M - £16.96M) = £17.6M / £15.04M = <strong>1.170</strong></p><p>The team needs to deliver £1.17 of value for every £1 spent for the remaining 55% of the project. Their current efficiency is £0.85 per pound.</p><p>That's a 38% improvement in cost efficiency. On a complex rail upgrade with entrenched subcontractor issues and ongoing design coordination problems, this isn't happening.</p><p>The honest conversation: "We need to re-forecast. The budget target is unachievable at current performance. Present a revised <a href="/en/earned-value/eac-etc-tcpi">EAC</a> with the EAC = BAC/CPI formula (£32M / 0.849 = £37.69M) and plan around a £5.69M overrun."</p></div><h2 id="tcpi-against-eac-the-alternative-denominator">TCPI Against EAC (The Alternative Denominator)</h2><p>There's a variant of TCPI that uses EAC instead of BAC in the denominator:</p><p><strong>TCPI (against EAC) = (BAC - EV) / (EAC - AC)</strong></p><p>This tells you the efficiency needed to hit the revised forecast, not the original budget. It's useful when the project has already re-baselined and you want to check whether the new EAC is achievable.</p><p>If TCPI against EAC is near 1.0, your forecast is consistent with current performance. If it's significantly above 1.0, even your revised forecast is optimistic.</p><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 happens when TCPI exceeds 1.20?</h3><p>In practice, the budget target is unachievable. A TCPI above 1.20 means you'd need to improve cost efficiency by 20% or more for all remaining work. That almost never happens without fundamental changes, different subcontractors, different methods, or a scope reduction. At this point, the conversation shifts from "how do we recover?" to "what's the realistic outturn?"</p><h3>How is TCPI different from CPI?</h3><p><a href="/en/earned-value/definitions/cost-performance-index">CPI</a> measures past performance: how efficiently have you been spending? TCPI measures required future performance: how efficiently must you spend going forward? CPI is diagnostic. TCPI is prescriptive. The gap between them tells you whether recovery is realistic.</p><h3>Should I report TCPI to the project board?</h3><p>Yes. It's the most intuitive metric for non-technical stakeholders. "We need to deliver £1.15 of value per pound when we've been averaging 87p" is immediately understood. CPI of 0.87 requires explanation. TCPI translates performance into a requirement everyone can grasp.</p><h3>Can TCPI be less than 1.0?</h3><p>Yes. If you're under budget (AC is well below EV), TCPI can be below 1.0, meaning you could actually underperform your budget rate and still hit the target. That's a healthy position, but it's rare on complex construction projects.</p></article></div>