Calculate Eac Using Graphic Calculator

What is Estimate at Completion (EAC)?

Estimate at Completion (EAC) is a crucial forecasting metric in project management used to predict the total cost of a project upon its completion. Unlike the Budget at Completion (BAC), which is a static budget set during the planning phase, EAC is a dynamic forecast that adjusts based on a project’s actual performance, including costs incurred and work completed. It gives project managers a realistic financial picture, helping to answer the critical question: “Based on our performance so far, what is the project likely to cost in total?”

This metric is a cornerstone of Earned Value Management (EVM), a methodology for objectively measuring project performance. While you could manually input formulas into a graphic calculator to find the EAC, this web-based tool automates the process, provides deeper insights, and visualizes the data for better decision-making.

The Formulas Behind the EAC Calculator

There isn’t a single way to calculate EAC. The best formula depends on your assumptions about the project’s future performance. This calculator supports the most common methods:

EAC = BAC / CPI: This formula is used when you assume that the cost performance to date will continue for the rest of the project. If your project has been consistently over or under budget, this method projects that trend forward.
EAC = AC + (BAC – EV): Use this when you believe that whatever caused past variances was a unique event and that the remaining work will be completed at the originally budgeted rate.
EAC = AC + [(BAC – EV) / (CPI * SPI)]: This is the most complex formula, factoring in both cost and schedule performance. It’s useful when you believe both time and money efficiencies (or inefficiencies) will impact the remaining work.

Variables Table

Description of variables used in EAC calculations.
Variable	Meaning	Unit	Typical Range
BAC (Budget at Completion)	The total, original budget for the entire project.	Currency ($)	Positive Value
AC (Actual Cost)	The total cost actually incurred to date.	Currency ($)	Positive Value
EV (Earned Value)	The value of the work performed to date.	Currency ($)	Positive Value
PV (Planned Value)	The budgeted cost of work scheduled to be completed.	Currency ($)	Positive Value
CPI (Cost Performance Index)	Measures cost efficiency (EV / AC). >1 is good, <1 is bad.	Ratio	0 to 2+
SPI (Schedule Performance Index)	Measures schedule efficiency (EV / PV). >1 is good, <1 is bad.	Ratio	0 to 2+

Practical Examples of EAC Calculation

Example 1: Project Over-Budget

A software development project has a BAC of $200,000. Halfway through, the team has spent $120,000 (AC) but has only completed work valued at $90,000 (EV). The project manager believes this cost overrun will continue.

Inputs: BAC=$200,000, AC=$120,000, EV=$90,000
Calculation: First, find CPI = EV / AC = $90,000 / $120,000 = 0.75. Then, use the formula EAC = BAC / CPI.
Result: EAC = $200,000 / 0.75 = $266,667. The project is now forecast to be over budget by $66,667.

Example 2: A Past Issue Corrected

A construction project with a BAC of $500,000 faced an early material delay, causing an initial cost spike. The AC is now $150,000, and the EV is $120,000. The project manager is confident the issue is resolved and the rest of the work will proceed as planned.

Inputs: BAC=$500,000, AC=$150,000, EV=$120,000
Calculation: Use the formula EAC = AC + (BAC – EV).
Result: EAC = $150,000 + ($500,000 – $120,000) = $150,000 + $380,000 = $530,000. The forecast shows the project will finish $30,000 over budget due to that early issue.

How to Use This EAC Calculator

Enter Core Values: Input your project’s Budget at Completion (BAC), Actual Cost (AC), Earned Value (EV), and Planned Value (PV).
Select the Formula: Choose the EAC formula from the dropdown that best represents your analysis of future project performance.
Calculate: Click the “Calculate EAC” button.
Interpret Results: The primary result is your new EAC. Below it, you’ll see key performance indicators (CPI, SPI) and variances (CV, SV) that provide context for the forecast. The chart visualizes your new EAC against the original BAC.

Key Factors That Affect Estimate at Completion

Scope Creep: Uncontrolled changes or additions to the project scope almost always increase costs and affect the EAC.
Resource Costs: Unexpected changes in labor rates, material prices, or equipment costs can significantly alter the EAC.
Team Performance: A team that is more or less productive than planned will directly impact the Cost Performance Index (CPI) and, therefore, the EAC.
Inaccurate Initial Estimates: If the original BAC was fundamentally flawed, the EAC will reflect a more realistic total cost as actual data becomes available.
Project Risks: Realized risks, such as technical issues or supplier delays, often add costs that need to be reflected in a new EAC.
Schedule Delays: A delayed project can increase costs due to extended overhead, labor, and resource usage, which impacts the EAC, especially when using the SPI-factored formula.

Frequently Asked Questions (FAQ)

What is the difference between BAC and EAC?: BAC (Budget at Completion) is the original, approved budget for the project, set at the beginning. EAC (Estimate at Completion) is a forecast of the final cost, calculated during the project based on actual performance. BAC is a static baseline, while EAC is a dynamic prediction.
What does a CPI of less than 1.0 mean?: A Cost Performance Index (CPI) below 1.0 indicates that the project is over budget. For every dollar spent, you are earning less than one dollar’s worth of completed work. This is a sign of cost inefficiency.
Can EAC be lower than BAC?: Yes. If the project is performing under budget (CPI > 1.0), the EAC will be lower than the BAC, indicating a potential cost saving at completion.
How would I calculate EAC on a graphic calculator like a TI-84?: You would first calculate your CPI or SPI by manually dividing the relevant numbers (e.g., EV / AC). Then, you would type in the full EAC formula you wish to use (e.g., BAC / CPI) using the stored variable for CPI to get the final number. This web calculator automates all those steps.
What is Variance at Completion (VAC)?: VAC is the difference between the original budget and the new forecast (VAC = BAC – EAC). A negative VAC indicates a projected budget overrun, while a positive VAC indicates a projected surplus.
When should I use the formula involving both CPI and SPI?: This formula is best when the project’s schedule performance is affecting its cost performance. For example, if being behind schedule is forcing you to pay for overtime or expedited shipping, both factors are relevant to the final cost forecast.
Is a high EAC always a bad thing?: Not necessarily. While it often indicates a budget overrun, it can also be the result of approved scope changes that added value to the project. The key is to understand *why* the EAC has changed from the BAC.
How often should I recalculate the EAC?: EAC should be recalculated at regular reporting intervals (e.g., weekly, monthly) or whenever a significant event occurs that could impact project costs. It is a living document, not a one-time calculation.

Related Tools and Internal Resources

Project ROI Calculator: Analyze the potential return on investment for your project.
Startup Burn Rate Calculator: Understand how quickly your company is spending its capital.
Critical Path Method Calculator: Identify the longest stretch of dependent tasks and measure the project duration.
Earned Value Management (EVM) Calculator: A comprehensive tool for all EVM metrics.
Three-Point Estimating Calculator: Use PERT analysis to estimate task durations more accurately.
Cost-Benefit Analysis Template: A framework for evaluating the viability of a project.

Estimate at Completion (EAC) Calculator

Estimate at Completion (EAC)