Total Float Consumption Index (TFCI) 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-concept">The Concept</a></li><li><a href="#the-diagram">The Diagram</a></li><li><a href="#why-tfci-is-a-leading-indicator">Why TFCI Is a Leading Indicator</a></li><li><a href="#worked-example-28m-water-treatment-plant">Worked Example: £28M Water Treatment Plant</a></li><li><a href="#how-to-calculate-tfci-in-practice">How to Calculate TFCI in Practice</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>The Total Float Consumption Index (TFCI) measures how fast your project is eating through its programme float. It's a leading indicator. By the time <a href="/en/earned-value/definitions/schedule-performance-index">SPI</a> drops below 0.90 and everyone starts panicking, the float has usually been gone for months. TFCI catches the problem earlier because float erosion happens before critical path impact. Think of float as a buffer. TFCI tells you how quickly that buffer is shrinking.</p><p>TFCI is part of the <a href="/en/earned-value/definitions">earned value definitions glossary</a>. For overall schedule performance measurement, see the <a href="/en/earned-value/cpi-spi">CPI and SPI formula page</a>.</p><h2 id="the-concept">The Concept</h2><p>TFCI compares the rate at which total float is being consumed against the rate at which it was expected to be consumed.</p><p><strong>TFCI = Actual Float Consumption Rate / Planned Float Consumption Rate</strong></p><p>Or expressed as a ratio:</p><p><strong>TFCI = (F₀ - Fₜ) / (F₀ - Fₚ)</strong></p><p>Where:</p><ul><li><strong>F₀</strong> = Total float at project start (from the baseline programme)</li><li><strong>Fₜ</strong> = Total float remaining at the current date (from the updated programme)</li><li><strong>Fₚ</strong> = Total float that was planned to remain at the current date (from the baseline)</li></ul><p>A TFCI of 1.0 means float is being consumed exactly as planned. Above 1.0 means you're burning float faster than expected. Below 1.0 means you're preserving float better than planned.</p><h2 id="the-diagram">The Diagram</h2><pre class="ge-ascii-diagram ge-anim">Float Burndown Chart ===================== Total Float (days) 35 ┤ │● 30 ┤│ ╲ ● = Actual float remaining ││ ╲ ○ ○ = Planned float remaining 25 ┤│ ○ ╲ ││ ╲ 20 ┤│ ○ ╲ ││ ●╲ 15 ┤│ ○ ╲ ││ ● 10 ┤│ ○ ╲ ││ ● Float gap widening 5 ┤│ ○ ● ← DANGER ZONE ││ ● 0 ┤│─────────────○──────●────── └┤────┬────┬────┬────┬────┬────┬── 0 2 4 6 8 10 12 Month Planned consumption rate: 35 days over 12 months = 2.9 days/month Actual consumption rate (month 8): (35-5) / 8 = 3.75 days/month Planned float at month 8: 35 - (2.9 × 8) = 11.7 days Actual float at month 8: 5 days TFCI = (35 - 5) / (35 - 11.7) = 30 / 23.3 = 1.29 ┌──────────────────────────────────────────┐ │ TFCI Interpretation │ │ │ │ &lt; 0.80 Float growing. Unusual. │ │ 0.80-1.00 Healthy. On or better plan. │ │ 1.00-1.10 Marginal. Watch closely. │ │ 1.10-1.30 Float eroding too fast. │ │ &gt; 1.30 Float crisis. CP impact imminent│ └──────────────────────────────────────────┘</pre><p>In this example, the project started with 35 days of total float. By month 8, only 5 days remain. At the current burn rate, the float will be exhausted by month 9.3. After that, any delay goes straight onto the critical path.</p><h2 id="why-tfci-is-a-leading-indicator">Why TFCI Is a Leading Indicator</h2><p>This is the key insight. Most schedule metrics are lagging. <a href="/en/earned-value/definitions/schedule-performance-index">SPI</a> tells you that progress is behind. <a href="/en/earned-value/definitions/time-estimate-at-completion">TEAC</a> tells you the revised completion date. But by the time these metrics flag a problem, the float has already been consumed and the delays are already on the critical path.</p><p>TFCI catches the problem upstream. Float erosion is the early warning. A TFCI of 1.25 at month 6 tells you the project is consuming its schedule buffer 25% faster than planned. SPI might still be at 0.96 because the float is absorbing the slippage. Everything looks fine. It isn't.</p><p>I've used float tracking on three major NEC4 programmes and each time the TFCI spiked 6 to 8 weeks before SPI dropped below the threshold. That's 6 to 8 weeks of earlier intervention. On a £30M project, those weeks are the difference between a manageable recovery plan and an expensive acceleration exercise.</p><h2 id="worked-example-28m-water-treatment-plant">Worked Example: £28M Water Treatment Plant</h2><span class="ge-worked-label">Worked Example</span><div class="ge-callout ge-anim"><p><strong>Scenario:</strong> A £28M NEC4 Option C water treatment works. The Accepted Programme at contract start shows 35 days of total float across the critical and near-critical paths. The programme is 18 months, starting June 2025.</p><p><strong>Float tracking over 10 months:</strong></p><div class="ge-table-wrap ge-anim"><table class="ge-table"><thead><tr><th>Month</th><th>Planned Float (days)</th><th>Actual Float (days)</th><th>TFCI</th></tr></thead><tbody><tr><td>0</td><td>35.0</td><td>35.0</td><td>--</td></tr><tr><td>2</td><td>31.1</td><td>30.0</td><td>1.28</td></tr><tr><td>4</td><td>27.2</td><td>24.0</td><td>1.41</td></tr><tr><td>6</td><td>23.3</td><td>17.0</td><td>1.54</td></tr><tr><td>8</td><td>19.4</td><td>9.0</td><td>1.67</td></tr><tr><td>10</td><td>15.6</td><td>2.0</td><td>1.70</td></tr></tbody></table></div><p>At month 6, the TFCI hit 1.54. SPI at that point was 0.94. The programme looked fine. But the commercial manager flagged the float erosion in the monthly report.</p><p>Investigation revealed:</p><ul><li>Mechanical installation was running 10 days behind on a near-critical path (consuming float, not affecting CP yet)</li><li>Concrete curing was taking 2 days longer per pour than programmed (cumulative effect across 8 pours = 16 days consumed)</li><li>Neither issue was on the critical path yet, so SPI was barely affected</li></ul><p><strong>By month 8:</strong> Float down to 9 days. TFCI at 1.67. The team implemented a recovery plan (weekend working on mechanical installation, accelerated curing with admixtures). Cost: £85,000.</p><p><strong>Had they waited until month 10:</strong> Float at 2 days. Any further slip becomes critical path delay. Recovery at that point would've required full acceleration. Estimated cost: £340,000.</p><p>Early TFCI monitoring saved approximately £255,000 in avoidable acceleration costs.</p></div><h2 id="how-to-calculate-tfci-in-practice">How to Calculate TFCI in Practice</h2><p>You need two things: a baseline programme with float values, and regular programme updates that report actual float remaining.</p><ol><li><strong>At project start:</strong> Record total float from the baseline Accepted Programme. This is F₀.</li><li><strong>At each programme update:</strong> Record the total float reported by the scheduling software. This is Fₜ.</li><li><strong>Calculate planned float remaining:</strong> F₀ - (planned consumption rate x elapsed time). The planned consumption rate assumes float is consumed linearly over the project (a simplification, but workable).</li><li><strong>Calculate TFCI</strong> using the formula above.</li></ol><p>Some teams use a more sophisticated approach: they extract the planned float profile from the baseline programme (which isn't linear because float consumption varies by phase) and compare against actual. That's more accurate but requires more effort.</p><h2 id="common-mistakes">Common Mistakes</h2><ol><li><strong>Only tracking critical path float.</strong> Total float exists on near-critical paths too. An activity with 3 days of float is one delay away from becoming critical. Track float across all paths within, say, 10 days of the critical path. That's where the next problem is hiding.</li><li><strong>Not establishing F₀ properly.</strong> If you don't record the baseline float at project start, you can't calculate TFCI later. Extract it from the Accepted Programme on day one and baseline it. This is a 10-minute job that pays dividends for 18 months.</li><li><strong>Ignoring negative float.</strong> When activities go into negative float, the programme is telling you the logic can't support the completion date. Some planners "fix" this by removing logic links. That hides the problem. Negative float is data. Don't suppress it.</li><li><strong>Confusing total float with free float.</strong> Total float is the time an activity can slip without delaying the project. Free float is the time an activity can slip without delaying its successor. TFCI uses total float because that's what relates to project completion.</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>Is TFCI a standard EVM metric?</h3><p>Not in the traditional ANSI/EIA-748 framework. It's a supplementary schedule metric that sits alongside SPI and <a href="/en/earned-value/definitions/to-complete-schedule-performance-index">TSPI</a>. Some organisations (particularly in the US DoD and UK rail sectors) have adopted it as part of their integrated schedule health assessment. It deserves wider use.</p><h3>How often should TFCI be reported?</h3><p>Monthly, aligned with your programme updates. If you're only updating the programme quarterly (which is too infrequent, but common), TFCI will miss the early signals. Monthly programme updates and monthly TFCI reporting give you the best chance of catching float erosion before it becomes critical path delay.</p><h3>Can TFCI be negative?</h3><p>No, but the float itself can go to zero. Once all float is consumed, further delays hit the critical path directly and TFCI stops being meaningful. At that point, you're tracking SPI and <a href="/en/earned-value/definitions/time-estimate-at-completion">TEAC</a> for schedule impact. TFCI's value is in the period before float runs out.</p><h3>What's a good TFCI target?</h3><p>Below 1.0 is ideal. Between 1.0 and 1.10 is acceptable on most projects. Above 1.20 for two consecutive months should trigger a formal float recovery review. The exact thresholds depend on how much starting float you had. A project that started with 50 days of float can tolerate a higher TFCI than one that started with 15 days.</p></article></div>