Estimate at Completion (EAC) using CPI Calculator
A professional tool to forecast project total costs based on current performance.
Select your project’s currency. This will not affect the calculation but will label the results correctly.
The total original budget planned for the project.
The budgeted cost of the work that has actually been completed to date.
The total cost actually incurred to complete the work so far.
Forecasted Estimate at Completion (EAC)
$120,000.00
Cost Performance Index (CPI)
0.83
Cost Variance (CV)
-$10,000.00
Estimate to Complete (ETC)
$60,000.00
EAC is calculated as Budget at Completion (BAC) divided by the Cost Performance Index (CPI).
What is Estimate at Completion (EAC) using CPI?
Estimate at Completion (EAC) is a crucial project management forecast that predicts the most likely total cost of a project upon completion. When you calculate EAC using CPI, you are using the project’s past cost efficiency to predict its future financial outcome. This method is a core component of Earned Value Management (EVM) and provides a realistic, data-driven assessment of the project’s budget trajectory.
The Cost Performance Index (CPI) is a ratio measuring the cost efficiency of the work completed. A CPI less than 1.0 indicates the project is over budget, while a CPI greater than 1.0 means it is under budget. This calculator uses that efficiency ratio (CPI) and applies it to the entire original budget (BAC) to generate the EAC. This specific formula assumes that the cost performance experienced so far will continue for the remainder of the project.
The Formula to Calculate EAC using CPI
The primary formula is straightforward, but it requires calculating the Cost Performance Index (CPI) first. The formulas are as follows:
1. Calculate CPI: CPI = EV / AC
2. Calculate EAC: EAC = BAC / CPI
This calculator also provides other useful metrics derived from these inputs, such as Cost Variance (CV = EV - AC) and Estimate to Complete (ETC = EAC - AC). A strong grasp of these metrics is essential for effective project cost control techniques.
| Variable | Meaning | Unit (Inferred) | Typical Range |
|---|---|---|---|
| BAC | Budget at Completion | Currency (e.g., $, €) | Positive value representing the total project budget. |
| EV | Earned Value | Currency (e.g., $, €) | Positive value representing the value of work done. |
| AC | Actual Cost | Currency (e.g., $, €) | Positive value representing the actual money spent. |
| CPI | Cost Performance Index | Unitless Ratio | Typically 0.5 to 1.5. <1 is over budget, >1 is under budget. |
| EAC | Estimate at Completion | Currency (e.g., $, €) | The forecasted total project cost. |
Practical Examples of EAC Calculation
Understanding how to calculate EAC using CPI is best illustrated with examples. The context of these numbers is critical for making informed project decisions.
Example 1: Project Running Over Budget
A software development project is struggling with unexpected technical debt, causing tasks to take longer and cost more than planned.
- Inputs:
- Budget at Completion (BAC): $200,000
- Earned Value (EV): $80,000 (40% of the work is done)
- Actual Cost (AC): $100,000
- Calculation Steps:
- Calculate CPI: $80,000 / $100,000 = 0.8
- Calculate EAC: $200,000 / 0.8 = $250,000
- Result Interpretation:
The CPI of 0.8 shows that for every dollar spent, only 80 cents of value was earned. If this trend continues, the project is forecasted to cost $250,000, which is $50,000 over the original budget. This is a critical insight for stakeholders. For more detail, one could consult an earned value management guide.
Example 2: Project Running Under Budget
A construction project benefits from lower-than-expected material costs and efficient crew performance.
- Inputs:
- Budget at Completion (BAC): $5,000,000
- Earned Value (EV): $2,500,000 (50% of the work is done)
- Actual Cost (AC): $2,000,000
- Calculation Steps:
- Calculate CPI: $2,500,000 / $2,000,000 = 1.25
- Calculate EAC: $5,000,000 / 1.25 = $4,000,000
- Result Interpretation:
The CPI of 1.25 indicates high cost efficiency. The project is earning $1.25 in value for every dollar spent. The forecast now shows the project can be completed for $4,000,000, saving $1,000,000 from the original budget. This might allow for reallocating funds or realizing profits.
How to Use This EAC Calculator
Using this calculator to calculate EAC using CPI is a simple process designed for accuracy and clarity.
- Select Currency: Choose the appropriate currency symbol from the dropdown. This ensures your results are labeled correctly.
- Enter BAC: Input the total planned budget for your project in the ‘Budget at Completion’ field.
- Enter EV: Input the value of the work completed to date in the ‘Earned Value’ field. This value represents the budget for the work you’ve done.
- Enter AC: Input the actual amount of money spent to achieve the completed work in the ‘Actual Cost’ field.
- Review Results: The calculator automatically updates in real-time. The primary result is the EAC, your new forecasted total project cost. Also, examine the intermediate values: CPI (your cost efficiency), CV (your current budget deficit/surplus), and ETC (the money needed to finish the project). For more on this, our Cost Variance calculator offers a deeper dive.
- Interpret the Chart: The bar chart provides an instant visual comparison between your original budget (BAC) and your forecasted cost (EAC), highlighting the projected overrun or underrun.
Key Factors That Affect EAC
The accuracy of the EAC forecast depends on several underlying factors. When you calculate EAC using CPI, you’re making an assumption of continued performance, which can be influenced by:
- Scope Creep: Uncontrolled changes or additions to the project scope will increase costs and make the original BAC irrelevant, directly impacting EAC.
- Resource Costs: Fluctuations in labor rates or material prices can significantly alter the AC, thereby changing the CPI and the final EAC.
- Risk Realization: If unforeseen risks occur (e.g., equipment failure, supply chain delays), the AC will increase, leading to a lower CPI and a higher EAC.
- Accuracy of Initial Estimates: If the original BAC was poorly estimated, the EAC calculation will be based on a flawed foundation.
- Team Productivity: A change in team efficiency (either improving or declining) will alter the relationship between work done (EV) and cost (AC), directly influencing the CPI.
- Data Accuracy: The EAC is only as good as the input data. Inaccurate tracking of EV or AC will lead to a misleading forecast. Understanding the Cost Performance Index formula is key to ensuring data quality.
Frequently Asked Questions (FAQ)
1. What is a “good” CPI value?
A CPI of 1.0 is “on budget.” A value greater than 1.0 is favorable (under budget), and a value less than 1.0 is unfavorable (over budget). A CPI of 0.8 means you’re getting 80 cents of value for every dollar spent, while a CPI of 1.2 means you’re getting $1.20 of value for every dollar spent.
2. What happens if my Actual Cost (AC) is zero?
If AC is zero, the calculator cannot divide by it and will show an error or an infinite result. An AC of zero means no money has been spent, so a performance calculation is not yet possible.
3. Can the EAC be lower than the Actual Cost (AC)?
No, this is not logically possible. EAC represents the total forecasted cost, which must include the money already spent (AC) plus the money needed to finish (ETC). Therefore, EAC will always be equal to or greater than AC.
4. When should I use this specific EAC formula (BAC / CPI)?
This formula is most appropriate when you believe the cost performance and efficiency demonstrated by the project so far are the most reliable indicators of future performance. It’s used when there’s no reason to assume the conditions will change for the remainder of the project.
5. How does this differ from the other EAC formulas?
Other common EAC formulas incorporate different assumptions. For example, `EAC = AC + (BAC – EV)` assumes future work will be performed at the originally planned rate. Another, `EAC = AC + [(BAC – EV) / (CPI * SPI)]`, considers both cost and schedule performance. To choose the right formula, you need to assess which assumption best fits your project’s reality. A related concept is the Schedule Performance Index calculator.
6. Do the units have to be in a specific currency?
No, the calculation is unit-agnostic as long as you are consistent. You can use any currency (or even abstract “cost units”) for BAC, EV, and AC. The EAC result will be in that same unit. This calculator provides a currency selector for labeling purposes only.
7. How often should I calculate EAC for my project?
You should calculate EAC at regular reporting intervals (e.g., weekly, bi-weekly, or monthly) as part of your project performance monitoring. The more frequently you track it, the earlier you can detect deviations and take corrective action.
8. What if my CPI is very low (e.g., 0.2)?
A very low CPI indicates a severe budget overrun. The resulting EAC will be extremely high. While mathematically correct, you should investigate the root cause. It might point to a catastrophic issue, a flawed data point, or suggest that the project is no longer viable without significant intervention.