Estimate at Completion (EAC): 4 PMP Formulas and When Each Applies
Most PMP candidates can write all four EAC formulas from memory. Most still miss the scenario questions. The formula memorization is not where candidates fail. Picking the right formula for the given situation is where points get lost.
PMI weights EVM heavily inside the Process domain, which makes up 50% of the exam. You will see multiple EAC questions. Every one gives you a scenario and expects you to select the right formula before you do the math. Correct arithmetic on the wrong formula scores zero.
This article gives you the decision rule that makes those questions reliable.
What EAC Measures
EAC stands for Estimate at Completion. It answers one question: based on what we know right now, what will this project cost when it finishes?
EAC is a forecast, not a final number. You are partway through a project, something has happened, and a stakeholder needs to know whether the original budget still holds. The four formulas exist because “what happens next” can mean four different things depending on the project situation.
The Framework Behind All Four Formulas
Every EAC formula is a version of the same idea:
EAC = AC + ETC
AC = Actual Cost. What you have spent so far.
ETC = Estimate to Complete. What it will still cost to finish.
The four formulas differ only in how they calculate ETC. Each one makes a different assumption about future performance. Once you see that, the formulas stop looking like random algebra.
Formula 1: EAC = BAC / CPI
This is the most common EAC formula on the exam. Use it when the question says the project “will continue at the current performance rate” or “past performance is expected to continue.”
CPI (Cost Performance Index) = EV divided by AC. If you are earning 80 cents of value for every dollar spent, this formula assumes that ratio will not change.
Example: BAC = $100,000. CPI = 0.8. EAC = $100,000 / 0.8 = $125,000.
The project will cost 25% more than planned if performance stays where it is.
Trigger phrase to watch: “will continue at current performance” or “CPI is expected to hold.”
Formula 2: EAC = AC + (BAC - EV)
Use this when the variance was a one-time event that will not repeat. The question will often say “the variance was atypical,” “the issue has been resolved,” or “this problem will not happen again.”
The logic: count what you have spent, then assume the remaining work runs exactly on budget.
BAC minus EV represents the remaining work, valued at the original plan.
Example: AC = $20,000. BAC = $100,000. EV = $15,000. EAC = $20,000 + ($100,000 - $15,000) = $105,000.
Trigger phrase: “atypical variance,” “one-time issue,” “problem has been resolved.”
PMI uses the word “atypical” often. When you see it, this formula applies almost every time.
Formula 3: EAC = AC + (BAC - EV) / CPI
Use this when the past variance was not a fluke and you expect cost performance to hold through the rest of the project.
The logic: the remaining work will be done at the same efficiency rate seen so far.
Example: AC = $20,000. BAC = $100,000. EV = $15,000. CPI = 0.75. Remaining work at budget = $85,000. Adjusted for ongoing CPI: $85,000 / 0.75 = $113,333. EAC = $20,000 + $113,333 = $133,333.
Trigger phrase: “the team will continue at the current CPI” or no mention of atypical variance and no schedule pressure noted.
This formula is closely related to Formula 1. Both assume the past CPI continues. The difference is that Formula 1 collapses the math into a single step.
Formula 4: EAC = AC + (BAC - EV) / (CPI x SPI)
Use this when both cost and schedule performance are hurting the project and the schedule slip is driving up costs. This shows up in questions where the team is falling behind on schedule AND spending more to try to recover.
SPI (Schedule Performance Index) = EV divided by PV.
If CPI = 0.8 and SPI = 0.9, the denominator becomes 0.72. A smaller denominator makes ETC larger, so the total EAC goes up.
Example: AC = $20,000. BAC = $100,000. EV = $15,000. CPI = 0.8. SPI = 0.9. EAC = $20,000 + $85,000 / (0.8 x 0.9) = $20,000 + $118,056 = $138,056.
Trigger phrase: “schedule slippage is affecting costs” or when both SPI and CPI are explicitly below 1.0 and the question ties them together.
This is the least common of the four. The exam uses it to test whether you understand that schedule delays and cost overruns can compound each other.
The Decision Rule
Before you calculate anything, find the trigger in the question:
| What the question says | Formula to use |
|---|---|
| “Will continue at current performance” | BAC / CPI |
| “Variance was atypical” or “issue resolved” | AC + (BAC - EV) |
| “Past CPI expected to continue” | AC + (BAC - EV) / CPI |
| “Schedule slip is driving up cost” | AC + (BAC - EV) / (CPI x SPI) |
No trigger? Use BAC / CPI. PMI treats it as the default assumption when the question does not specify how future performance will behave.
ETC Is Not EAC
ETC is the amount you still need to spend to finish the project. EAC is the total cost at project end.
The relationship: EAC = AC + ETC, which means ETC = EAC minus AC.
If the question asks for “remaining cost” or “estimate to complete” and you give back the full EAC number, you lose the point. Read the question carefully. “Remaining” and “total” are the tells.
Practice Question
A project has a BAC of $80,000. Midway through, the project reports: AC = $50,000, EV = $40,000. The project manager notes the overrun was caused by an unexpected equipment failure that has now been corrected. What is the EAC?
Step 1: Find the trigger. “Unexpected…now corrected” signals a one-time event. Step 2: Use Formula 2. EAC = AC + (BAC - EV) = $50,000 + ($80,000 - $40,000) = $90,000.
Compare to Formula 1: CPI = 40,000 / 50,000 = 0.8. EAC = $80,000 / 0.8 = $100,000.
Two answers. Both correct arithmetic. One right choice. The clue word is the difference.
What PMI Is Actually Testing
PMI does not want to know whether you can multiply. It wants to know whether you can read a project situation and select the right assumption about the future. That is a judgment skill.
The fastest path to getting these questions right: read the scenario fully, find the clue phrase, then do the math. Candidates who go straight to the numbers tend to default to Formula 1 and miss the trigger sitting two sentences earlier.
Work the clue first. The arithmetic follows.
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