What is estimate at completion (EAC)? Formulas, examples, and project tracking for 2026

Most project budgets don’t fail in one dramatic moment. They drift. A delayed shipment here, a scope change there, until the final cost sits well above the plan. Estimate at completion (EAC) is the forecasting metric that catches that drift early, giving you a running prediction of what a project will actually cost once it’s finished.

This guide breaks down the four EAC formulas, when to use each one, and how to plug in real numbers with worked examples. You’ll also see how to keep forecasts accurate as conditions change, and how monday’s AI Workspace can calculate cost performance for you instead of leaving it buried in spreadsheets. With AI-powered agents that surface budget risks automatically and dashboards that track CPI in real time, the platform turns EAC from a periodic calculation into a continuous early-warning system that updates as your project moves.

Key takeaways

• Estimate at completion (EAC) forecasts a project’s total cost based on actual performance to date, not just the original budget

• Four standard EAC formulas exist, and the right one depends on whether performance is steady, hit by a one-time variance, or affected by both cost and schedule problems

• Calculating EAC regularly and comparing it to budget at completion (BAC) helps you spot overruns while you still have time to act

• Related metrics such as ETC, TCPI, and VAC add context by showing remaining cost, the efficiency you’d need to hit budget, and total forecast variance

• monday AI Workspace tracks cost data in real time, calculates performance indexes automatically, and flags budget overruns before they compound

What is estimate at completion (EAC)?

EAC stands for estimate at completion: the current expectation of a project’s total cost once it’s finished. The calculation is the sum of the amount invested at the time of measurement and the costs necessary to complete the work. It’s a core metric in earned value management (EVM), a project performance method that integrates scope, schedule, and cost.

When unforeseen events crop up, such as delays or unplanned expenses, managers use an EAC to reassess the total costs required to complete the project. In this context, an EAC helps stakeholders measure the impact of changes more accurately and manage available resources better.

A fundamental observation needs to be made: don’t confuse Estimate at Completion with Estimate to Completion, short for ETC. The former calculates accrued and expected costs, while the latter refers only to the expected costs to complete the project. That said, it’s important to understand the relationship between an EAC and a BAC, also known as Budget at Completion.

EAC vs ETC, BAC, TCPI, and VAC: how the cost metrics connect

Both EAC and BAC are cost calculations, though for different project periods. While EAC deals with the final cost forecast of a project that’s already underway, BAC deals with the cost that was authorized at the beginning of the project – the original budget.

In practice, EAC evolves as it accounts for unforeseen circumstances and financial variations, and it is calculated at various points throughout the project life cycle. BAC, on the other hand, is static, used as a parameter to define the earned value, or EV, of the project.

An example: a team calculates $100,000 as the BAC for a 1-year project. After 3 months, scheduling delays impact the project, and the team needs more resources to complete everything on time. With the added costs, the team creates a new budget, and the project cost estimate is $160,000.

In this case, it’ll be necessary to spend $60,000 more than initially anticipated, making the EAC larger than the BAC. Keep in mind, in this example, there are still 9 months to complete the project, and other unforeseen events may occur, necessitating a new EAC. In such cases, the project manager’s challenge is to mitigate the impact of actionable expenses, reallocate resources, and increase the team’s performance.

EAC rarely travels alone. To read a cost forecast well, it helps to see how it relates to the other earned value metrics that describe the same project from different angles. The table below distinguishes the five you’ll use most often.

A few plain-language definitions make the table easier to apply. ETC is simply everything you still expect to spend, so it’s the forward-looking half of EAC once you strip out actual cost. TCPI answers a sharper question: to land on the original budget, how efficient must the remaining work be? A TCPI above 1.0 means you’d need to outperform your plan, which is a warning sign. VAC closes the loop by turning EAC into a single variance figure: a negative number signals a projected overrun, and a positive one signals savings.

Four estimate at completion formulas and when to use each

There isn’t one estimate-at-completion formula. There are four, and the one you choose depends on what’s actually happening on the project. Before the formulas, it helps to have the variables straight, since every calculation draws from the same short list of earned value inputs.

With those defined, here are the four most common formulas for calculating EAC:

• EAC = AC + ETC: This formula is the most generic and is often used when BAC is estimated from inaccurate or erroneous data. In this case, the EAC represents the sum of Actual Cost (AC) and Estimate to Completion (ETC)

• EAC = BAC / CPI: This is the most recommended calculation when the project is in progress, and no interference is expected. To check the EAC, divide the BAC by the Cost Performance Index (CPI)

• EAC = AC + BAC – EV / CPI x SPI: This is the formula used when schedule delays and expenses increase. In this case, it’s necessary to add the Schedule Performance Index (SPI) and the Earned Value (EV) to the equation

• EAC = AC + (BAC – EV): Use this formula when unforeseen events are overcome, and you believe no new interference will occur until the end of the project

Choosing between them comes down to your read on the project. Match the formula to the situation using this quick guide:

• AC + ETC: use when your original estimate is obsolete, and you need to rebuild the remaining cost from a fresh, bottom-up estimate

• BAC / CPI: use when performance has been steady, and you expect current cost efficiency to hold for the rest of the work

• AC + (BAC − EV): use when a one-time variance has hit, but you’re confident the rest of the plan will run at the budgeted rate

• AC + [(BAC − EV) / (CPI × SPI)]: use when both cost and schedule are slipping, so the forecast has to account for combined pressure

For more on how earned value management uses these performance trends to forecast final project costs and completion dates, this APMG earned value management guidance is a useful reference. Whichever formula you pick, the quality of the answer depends on the quality of the BAC behind it. There are endless variables that impact costs in project management and, in turn, the calculations of the EAC.

The biggest impact, however, comes from the initial BAC calculations, so it pays (quite literally) to be diligent when tracking and categorizing costs during the project planning stage. With a robust BAC in place, EAC calculations are more accurate and help keep projects on track and within budget.

How to calculate EAC: a worked example

To calculate Estimate at Completion, gather your actual cost, earned value, and budget, work out the performance indexes, then plug them into the formula that fits your situation. Two worked examples show how the numbers move.

In the first scenario, performance is steady, so the BAC / CPI formula applies. A team is running a $100,000 project and wants a mid-point forecast.

First, calculate the cost performance index: CPI = EV / AC = $48,000 / $60,000 = 0.8. A CPI below 1.0 means the team is spending faster than it’s earning value. Now apply the formula: EAC = BAC / CPI = $100,000 / 0.8 = $125,000. At the current pace, the project is forecast to finish $25,000 over budget, which signals the need to act now rather than at closeout.

The second scenario is harder, because both cost and schedule are slipping. That calls for the formula EAC = AC + [(BAC − EV) / (CPI × SPI)].

Start with CPI = EV / AC = $100,000 / $120,000 ≈ 0.83. Multiply the two indexes: CPI × SPI = 0.83 × 0.90 = 0.75. Then work out the remaining budgeted work: BAC − EV = $200,000 − $100,000 = $100,000. Divide it by the combined index: $100,000 / 0.75 ≈ $133,333. Finally, add the actual cost: EAC = $120,000 + $133,333 ≈ $253,333. The forecast overrun is about $53,333, which is the project’s variance at completion (VAC = BAC − EAC).

Using EAC to track project performance

So far, we have seen how EAC is necessary to realistically guide a project through uncertain scenarios. If you want the best chance of success in the face of uncertainty, EAC is an excellent metric for monitoring project performance. Because EAC forecasts the final cost based on the information available at the time, it’s not enough to use it reactively. You should also use EAC proactively.

Another strategy is to analyze the EAC together with other important KPIs, such as the BAC – mentioned before – and the CPI, short for the Cost Performance Index. The CPI calculates the difference between the EV and the actual cost, or AC, at the present moment.

The CPI, which should also be calculated regularly, shows how efficiently the project budget is being spent. By tracking these metrics, stakeholders know how well teams are performing and can reallocate resources to the tasks and activities that need them at that moment. These methods and calculations also help identify potential roadblocks that can seriously impact project success, among many other benefits.

Benefits of an evolving EAC model

There’s no single method of calculating the Estimate at Completion. But for a reliable result, use the formula that best fits your finances. At the same time, you may need to refine your calculations during the project life cycle, which is called an “evolving EAC model.” Agility in the way you calculate EAC has several benefits:

• Helps ensure earned value: Calculating the EAC along with other indicators enables you to develop new strategies that offset and prevent the accumulation of negative impacts on the project’s EV

• Identify waste: Calculating EAC regularly helps detect areas of overspending, which can impact project progress (read: no more budget overruns)

• Better allocate resources: An adaptive EAC model helps stakeholders understand priorities and identify opportunities to allocate resources, whether by adjusting budgets across teams or changing team structures

• Minimize risk: EAC provides a more accurate way to estimate your project’s actual costs and reduce risk throughout the project lifecycle

To better understand the benefits, let’s explore how an EAC calculation can help a project handle unexpected expenses.

Using EAC to adapt a project when new expenses arise

Imagine that you’re working at a medium-sized civil engineering company and you’re managing a new venture. The initial timetable forecasts a year of work divided into four quarters. The Budget at Completion is $700,000, including all resources (break it down into actual hours) and material costs. The project plan indicates that $400,000 of the budget will be spent during the first quarter, with the remaining $300,000 divided evenly over the last three quarters.

With strong investment in the first stage, the team starts with a bang. But after a month of progress, a government agency fines the company for a regulatory oversight related to the project and suspends work for four weeks. In this new reality, the EAC calculation needs to consider these variables:

• How much of the budget was spent so far

• A new timeline accounting for the interruption

• Any additional costs required to complete the first stage

• The costs of the fine

• The cost required to complete the next stages given the changes

• Any other loss of resources due to work interruption, such as employees leaving the company

This example illustrates the importance of the BAC since the overall objective is to keep the EAC lower than the BAC. Therefore, it’s critical to set aside a portion of your project’s budget to account for the unexpected when creating the project management plan. This budget buffering can help you reduce waste, avoid resource cuts, and distribute remaining resources more effectively.

Great project planning, budgeting, and knowing how and when to use an EAC will help you keep your projects on track and moving toward success. But these activities are only as good as the platform you use to do them.

Six best practices for accurate EAC tracking

An EAC is only as trustworthy as the data and discipline behind it. Teams that forecast well treat EAC as routine, not a fire drill, and standardize how the number is produced. These six practices, alongside disciplined project cost tracking, keep your forecasts honest as the project changes.

1. Automate data collection: pull actual cost and status from where the work already lives instead of copying figures by hand, which cuts lag and transcription errors

2. Recalculate on a fixed cadence: set a weekly or biweekly rhythm rather than waiting for something to break, so drift shows up while it’s still small

3. Base estimates on CPI and SPI: ground your forecast in measured cost and schedule efficiency, not gut feel, and match the formula to what those indexes reveal

4. Blend top-down and bottom-up ETC: cross-check a high-level forecast against a task-by-task estimate of remaining work to catch gaps either view misses

5. Document your assumptions: record what each estimate assumes about scope, rates, and risks, so you can easily trace a shift in reality to a revised number

6. Communicate updates to stakeholders: share each recalculated EAC and its variance promptly, so decisions about scope, budget, and resources happen early

The first two practices are where a connected work platform earns its keep. Automations can trigger a fresh calculation the moment an actual cost or status changes, and a shared dashboard keeps CPI visible to everyone without a manual refresh.

How monday AI Workspace supports estimate-at-completion tracking

The hardest part of EAC tracking isn’t the math. It’s keeping the inputs current. When actual cost lives in one spreadsheet, the schedule in another, and earned value in a third, every forecast starts with hours of reconciliation, and the number is stale the moment it’s finished. That gap between reality and your last calculation is exactly where overruns hide.

monday AI Workspace closes that gap by keeping cost, progress, and schedule data connected in one place, then layering AI on top to forecast and flag. The table below contrasts the manual approach with tracking EAC on monday AI Workspace.

Several capabilities do the heavy lifting. Dashboards act as the intelligence layer, turning work data into real-time views with numeric goal tracking, progress battery views, Gantt timelines, and portfolio-level executive summary reports, so AC, EV, CPI, and EAC stay visible over time. Automations remove manual refreshes by triggering a recalculation or alert the moment an actual cost or status changes, keeping CPI and EAC current between reviews.

AI extends the same data further. monday agents can run specialized cost work end to end. A custom agent built to total budget overrun requests by department and quarter can route them to the right analyst and post a weekly coverage summary, while the prebuilt Risk Analyzer surfaces schedule and delivery risks that feed the schedule side of your forecast. These agents work alongside your team, handling the repetitive tracking so people can focus on the decisions. For plain-language access, monday sidekick lets you ask for a project’s current cost position in the flow of work, and Sidekick returns the figure without building a report. When you’re ready to standardize the setup, proven cost estimation techniques give you a starting structure for reliable estimates.

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Turning cost forecasts into confident decisions

Estimate at completion earns its place because it turns a project’s messy, mid-flight reality into a single number you can act on. The point isn’t the formula. It’s the lead time. A forecast that shows a $25,000 overrun in month three gives you room to renegotiate scope, shift resources, or reset expectations while those moves still matter.

The teams that stay ahead of overruns are moving away from reactive, once-a-quarter spreadsheet checks toward continuous, AI-assisted forecasting that updates as the work does. Paired with a dependable cost management platform, a living EAC stops being a closeout autopsy and becomes an early-warning system your whole team can trust.