What is Estimate at Completion (EAC)?
Estimate at Completion is the forecast of what the whole project will actually cost, given performance so far. The workhorse formula divides the total budget by the cost performance index — if you're getting 83 cents of value per dollar, the whole job costs proportionally more.
The exam tests formula selection more than arithmetic: use BAC ÷ CPI when current spending patterns will continue; use AC + (BAC − EV) when the overrun was a one-time event and future work will go to plan.
Formula
EAC = BAC ÷ CPI (typical case)
Worked example
BAC = $100,000 and CPI = 0.83. EAC = 100,000 ÷ 0.83 ≈ $120,500. If current cost efficiency continues, the project will finish roughly $20,500 over its original budget.