Predicting the future in project management isn’t magic; it’s Forecasting. By using your current performance trends, you can calculate your final bill and your true finish date before they happen.
1. The Big Question: What will the total cost be? (EAC)
The Estimate at Completion (EAC) is your forecast of the total cost of the project when it is finished.
Depending on how your project is going, there are two main ways to calculate this:
Scenario A: Your current performance is the “New Normal”
If you’ve been over budget because of a systemic issue (like rising material costs) and you expect that trend to continue, use this formula:
The Formula:
EAC = BAC/CPI
(Note: BAC is your original “Budget at Completion”)
Example: Your budget was $100,000. Your CPI is 0.80 (you’re spending $1 to get $0.80 of value).
Forecast: $100,000 / 0.80 = $125,000.
Scenario B: The “Oops” Moment (One-time Variance)
If you went over budget because of a one-time accident, but you expect the rest of the project to go exactly as planned, use this:
The Formula:
EAC = AC + (BAC – EV)
2. How much more money do I need? (ETC)
The Estimate to Complete (ETC) tells you how much additional cash you need to cross the finish line from this moment forward.
The Formula:
ETC = EAC – AC
- Why it matters: This is the number you take to your Finance Director when you need to request more funding. It’s precise, backed by data, and leaves no room for “guessing.”
3. The “Stress Test”: To-Complete Performance Index (TCPI)
The TCPI is the most honest metric in project management. It tells you exactly how efficient your team must be from now on to finish within your original budget.
The Formula:
TCPI = {BAC – EV}/{BAC – AC}
How to Read the TCPI “Stress Score”:
- TCPI < 1.0: You have a “cushion.” You can work less efficiently and still hit the budget.
- TCPI = 1.0: You must work exactly to your original plan.
- TCPI > 1.1: Danger Zone. Your team must work significantly harder or faster than originally planned to make up for past losses. This is often where scope needs to be cut.
Forecasting Cheat Sheet
| Metric | What it Tells You | The Formula |
| EAC | The total final bill. | BAC / CPI |
| ETC | How much more cash we need today. | EAC – AC |
| TCPI | How hard we need to work to recover. | (BAC – EV) / (BAC – AC) |
Summary
Forecasting isn’t about being a pessimist; it’s about being a proactive leader. When you can show a stakeholder a TCPI of 1.25, you aren’t just “complaining” that the project is hard—you are providing mathematical proof that the current plan is unsustainable.
