EAC vs. ETC Explained — For Practicing Project Managers, Not PMP Exams

Every article about EAC and ETC is written for the PMP exam. They give you formulas, acronyms, and abstract examples about building a warehouse.

That's not helpful when you need to tell your SteerCo next Tuesday what this project will actually cost when it's done.

This guide is written for practicing project managers who need to calculate, explain, and act on EAC and ETC in real professional services engagements—not pass a certification test.

The Plain-Language Definitions

EAC (Estimate at Completion): What will this project cost when it's done?

ETC (Estimate to Complete): How much more do we need to spend to finish?

That's it. The relationship between them is simple:

EAC = Actual Cost to Date + ETC

Or rearranged:

ETC = EAC - Actual Cost to Date

If you've spent $200K so far and you estimate you need another $150K to finish, your EAC is $350K and your ETC is $150K.

The complexity isn't in the definitions—it's in figuring out the right number to put in.

Why EAC/ETC Matter in Professional Services

In professional services, EAC answers the question your leadership cares about most: "Is this project going to make money, and how much?"

You signed a SOW for $400K in revenue. You budgeted $160K in costs for a 60% gross margin. You're now four months in and you've spent $120K. The question isn't "are we on budget for Month 4?"—it's "what will the total cost be when we're done, and what does that mean for margin?"

EAC also drives critical decisions:

• Should we pursue a change order?
• Do we need to renegotiate scope?
• Is this project worth continuing?
• What do we tell the client about budget burn?

Without an accurate EAC, you're guessing. And in my experience managing eight-figure delivery portfolios, guessing leads to unpleasant surprises.

The EAC Formulas: When to Use Each One

The PMP materials give you four formulas. Here's when each one actually applies in professional services:

Formula 1: EAC = AC + Bottom-Up ETC

When to use: When past performance isn't predictive of future performance, and you have the ability to re-estimate remaining work.

What it means: Throw out the budget-based forecasting. Have your team re-estimate every remaining work item from scratch.

Professional services example:

You're running a software implementation. The original estimate assumed 300 hours of integration work. Halfway through, you discover the client's legacy system has undocumented APIs that require triple the effort. Past performance is irrelevant—you need a fresh estimate for what remains.

You gather the team, re-estimate the remaining 15 work items, and arrive at 450 hours of remaining work at $85/hr blended cost = $38,250 ETC.

Add that to the $62,000 already spent: EAC = $100,250.

Pros: Most accurate when circumstances have fundamentally changed. Cons: Time-consuming. Requires detailed work breakdown.

Formula 2: EAC = AC + (BAC - EV) / CPI

When to use: When the cost variance you're experiencing is typical—meaning you expect the same level of over/under-performance to continue.

What it means: Adjust remaining budget by your current cost performance efficiency.

Breaking down the acronyms:

• AC = Actual Cost to date
• BAC = Budget at Completion (original total budget)
• EV = Earned Value (budgeted cost for work actually completed)
• CPI = Cost Performance Index (EV / AC)

Professional services example:

You're running a data migration project budgeted at $200K cost (BAC = $200,000).

Four months in:

• You've spent $95,000 (AC = $95,000)
• You've completed work that was budgeted at $80,000 (EV = $80,000)
• Your CPI = $80,000 / $95,000 = 0.84 (you're getting 84 cents of value for every dollar spent)

Remaining budgeted work: $200,000 - $80,000 = $120,000

Adjusted for your efficiency: $120,000 / 0.84 = $142,857

EAC = $95,000 + $142,857 = $237,857

Your project will cost $38K more than budgeted if current performance continues.

Pros: Quick to calculate. Uses actual performance data. Cons: Assumes past performance predicts future performance.

Formula 3: EAC = AC + (BAC - EV)

When to use: When the variance is atypical—a one-time issue that won't recur.

What it means: Keep the original estimate for remaining work and just add what you've already overspent.

Professional services example:

Your project hit a one-time snag: a key resource was pulled for two weeks to handle a client escalation, and you had to bring in an expensive contractor to cover. That cost you an extra $15,000.

But that's done now. The contractor is off the project. Going forward, you expect normal performance.

• AC = $75,000 (including the $15K overage)
• EV = $60,000
• BAC = $150,000

EAC = $75,000 + ($150,000 - $60,000) = $165,000

You're over by $15K, but you don't expect further variance.

Pros: Simple. Appropriate for isolated issues. Cons: Dangerous if you're wrong about the variance being one-time.

Formula 4: EAC = (AC + ETC) Using Blended CPI and SPI

When to use: When both cost and schedule performance are important, and you want to factor in both.

This gets into more complex territory (SPI = Schedule Performance Index), and honestly, for most professional services projects, Formulas 1-3 cover the use cases. If you're in a situation where schedule variance significantly impacts cost (milestone-based payments, liquidated damages), you may need this.

For most T&M or fixed-price consulting engagements, focus on cost performance.

A Complete Professional Services Example

Let's walk through a realistic scenario end-to-end.

The Situation:

You're managing a CRM implementation engagement for a financial services client.

• Contract value: $480,000 (fixed price)
• Budgeted cost: $200,000
• Budgeted gross margin: 58.3%
• Duration: 10 months
• Current month: Month 4

Month 4 Status:

Performance Indices:

• CPI = EV / AC = $70,000 / $98,000 = 0.71
• SPI = EV / PV = $70,000 / $80,000 = 0.875

Translation:

• You're getting 71 cents of value for every dollar spent (cost overrun)
• You're 12.5% behind schedule (schedule slippage)

EAC Calculation:

The cost variance appears systemic—your team is consistently taking longer than estimated, and you don't see that changing. Use Formula 2:

EAC = AC + (BAC - EV) / CPI EAC = $98,000 + ($200,000 - $70,000) / 0.71 EAC = $98,000 + $183,099 EAC = $281,099

Impact Analysis:

Your project is still profitable at the forecasted EAC—but margin has dropped from 58% to 41%. On a $480K engagement, that's $81K less profit than planned.

ETC Calculation:

ETC = EAC - AC = $281,099 - $98,000 = $183,099

You need $183K more to finish, against a remaining budget of $102K. You're short by $81K.

How to Present EAC/ETC to Stakeholders

Your SteerCo doesn't want a formula walk-through. They want to understand: Are we okay? If not, what are we doing about it?

The Structure:

1. Current Position (30 seconds)

   • "We're 4 months into a 10-month engagement. We've spent $98K against a budget of $200K."

2. Forecast (30 seconds)

   • "Based on current performance, we forecast total cost of $281K—$81K over budget."

3. Impact (30 seconds)

   • "This would reduce gross margin from 58% to 41%. The project is still profitable, but we're leaving significant margin on the table."

4. Root Cause (60 seconds)

   • "The main driver is integration complexity. The client's legacy system has required 40% more effort than estimated. This is systemic, not a one-time issue."

5. Options and Recommendation (90 seconds)

   • "Option A: Continue as-is and absorb the margin hit. Option B: Pursue a change order for the integration complexity—estimated $60K. Option C: Descope the reporting module to offset integration overage. We recommend Option B because [rationale]."

The Slide:

Status: YELLOW

Root Cause: Integration complexity exceeding estimate

Recommended Action: Pursue change order for integration scope

What Not to Do:

• Don't present EAC as a single point estimate without context. Leadership will ask "how confident are you?" Be ready with a range.
• Don't present the number without a recommendation. You're the PM—own the path forward.
• Don't wait until the variance is unrecoverable. If you're forecasting an $80K overrun, the time to surface it is now, not three months from now when it's $120K and too late to change course.

Common EAC Mistakes in Professional Services

Mistake 1: Using the Wrong Formula

If your variance is one-time but you use Formula 2, you'll overstate the EAC. If your variance is systemic but you use Formula 3, you'll understate it.

Fix: Diagnose the nature of the variance before choosing a formula. Is this a one-time hit or an ongoing pattern?

Mistake 2: Gaming CPI with Scope Manipulation

Some PMs artificially inflate Earned Value by claiming work is "complete" that really isn't. This makes CPI look better and EAC look lower—until reality catches up.

Fix: Define clear completion criteria for work items. Use objective measures (deliverable accepted, code deployed) not subjective ones (developer says it's "done").

Mistake 3: Ignoring Leading Indicators

EAC based on CPI is a lagging indicator. By the time your CPI shows trouble, you've been burning money inefficiently for weeks.

Fix: Track leading indicators: team velocity, defect rates, hours logged vs. forecast this week. These give you early warning before EAC degrades.

Mistake 4: Re-Baselining to Hide Variance

When variance gets uncomfortable, some PMs "rebaseline" the budget to make EAC look better. The forecast looks great because you've just redefined what success means.

Fix: Keep the original baseline sacred. If you need to rebaseline (scope change, change order), document why and preserve the original for comparison.

Mistake 5: Presenting EAC Without Confidence Intervals

A point estimate of $281K isn't the whole story. What's the range? Is it $270K-$290K (high confidence) or $250K-$350K (lots of unknowns)?

Fix: Provide a range: "Our most likely EAC is $281K, with a range of $260K-$310K depending on remaining integration unknowns."

EAC Tracking Without Manual Calculations

Calculating EAC manually works for a single project. It breaks down when you're managing a portfolio of 15 projects and need to report aggregate EAC and margin impact to leadership weekly.

MyProjectBudget surfaces EAC and financial forecasting in real-time dashboards. As your team logs time and PMs update monthly forecasts, the system calculates EAC automatically—at the project level and rolled up across your portfolio.

No spreadsheet gymnastics. No formula errors. No waiting for month-end close.

EAC and ETC aren't academic exercises. They're the difference between knowing in Month 4 that you have a problem and discovering in Month 10 that you lost $80K.

The formulas matter less than the discipline: forecast early, forecast often, and act on what the numbers tell you.

Ready to stop calculating EAC in spreadsheets? Start a free trial of MyProjectBudget and get real-time financial forecasting for every project in your portfolio.