What it means
When you kick off a project, you create a baseline budget. However, as work progresses, reality sets in.
Materials cost more, tasks take longer, or scope changes happen. Estimate at Completion, often called EAC, takes your original plan and updates it based on actual performance to date.
Why does this matter for non-finance managers? Waiting until a project ends to check the final cost is too late.
EAC lets you see the financial destination before you arrive. If the projected final cost is higher than your original budget, you can take corrective action early, such as cutting non-essential tasks or renegotiating supplier rates.
In practice, project managers review EAC monthly. They look at what has been spent so far, known as actual costs, and evaluate how efficiently the team has worked.
Using this data, they recalculate the remaining expenses and add them together to form the new total forecast. By tracking this metric regularly, you avoid nasty financial surprises at project wrap-up.
It builds trust with stakeholders because you always provide realistic forecasts rather than blindly hoping the original budget will somehow hold. Think of a long car journey.
Halfway through, you check your fuel gauge and traffic app, and you realise you are burning petrol faster than expected, so you calculate a new total fuel cost to reach your destination.
In practice
Real-world examples
Example 1
You budgeted $10,000 to build a prototype website. After spending $4,000, you realise development is taking longer than expected, because the designer needed three rounds of changes. Your new Estimate at Completion is $12,000, so you tell the sponsor now rather than at launch.
Example 2
Your small manufacturing firm budgeted $50,000 for raw materials for a new product line. Due to supply chain delays, material costs rise by about 16% on the orders still to be placed. Your updated Estimate at Completion is $58,000, and you decide to approach a second supplier.
Example 3
An events agency budgeted $20,000 for an annual client gala. Midway through planning, venue hire fees increase. The team recalculates, resulting in an Estimate at Completion of $23,500, and they agree with the client to simplify the catering menu to bring the figure back down.
Think of it
Driving a long distance car journey. Halfway through, you check your fuel gauge and traffic app. You realise you are burning petrol faster than expected, so you calculate a new total fuel cost to reach your destination.
Formula
Calculation
EAC = Actual Cost + (Budget at Completion - Earned Value) / Cost Performance Index
Earned Value is the budgeted value of the work actually completed. The Cost Performance Index (CPI) is Earned Value divided by Actual Cost, so a CPI below 1.0 means you are spending more than the work is worth.
Numeric Example: your original budget (Budget at Completion) is $10,000. You have spent $4,000, but the work completed is only worth $3,200 of the budget, so the CPI is 3,200 / 4,000 = 0.8 because you are overspending.
Remaining work value = 10,000 - 3,200 = $6,800.
Adjusted remaining cost = 6,800 / 0.8 = $8,500.
EAC = 4,000 + 8,500 = $12,500.
The forecast overrun is $12,500 - $10,000 = $2,500. If you believe the overspend was a one-off and the remaining work will cost its budgeted amount, you would instead use EAC = Actual Cost + Remaining Budgeted Work = 4,000 + 6,800 = $10,800. Choosing between the two is a judgement about whether the inefficiency will continue.Case study
Seen in the real world
This is a fictional, illustrative scenario. BrightSpark Digital, a growing marketing agency, secured a contract to design a major e-commerce platform for a retail client. The agreed project budget was $60,000, scheduled over three months. At the end of month one, the project manager reviewed the financials.
The team had already spent $25,000, which was higher than the planned $20,000 due to unexpected technical hurdles with the database integration. Instead of ignoring the variance, the manager calculated the Estimate at Completion. The month-one work completed matched the plan, so it was worth $20,000, and the cost performance index was $20,000 divided by $25,000, or 0.8. Dividing the original budget by that index, $60,000 / 0.8, showed the project would ultimately cost $75,000 instead of $60,000.
Armed with this insight, the manager approached the client early in month two. They agreed to scale back a secondary feature to save $8,000 and split the remaining $7,000 variance, so each side absorbed $3,500. This proactive approach kept the project profitable and maintained a strong client relationship.
Watch out
Common mistakes
- Assuming the original budget is still accurate just because the project is only halfway through.
- Forgetting to include hidden costs like overtime or contractor rate increases in the remaining forecast.
- Failing to update the calculation regularly as project conditions change.
Questions
People also ask
How often should I calculate Estimate at Completion?
You should recalculate it at least monthly, or whenever a major change happens to the project scope.
Is Estimate at Completion the same as the original budget?
No. The original budget is what you planned to spend at the start. EAC is your latest prediction of what you will actually spend by the end.
What causes the Estimate at Completion to change?
Changes in labour rates, unexpected delays, scope creep, or efficiency issues will cause the EAC to rise or fall.