Work out your Cost Performance Index in seconds. Enter earned value and actual cost, and get your CPI, cost variance, and a plain-English read on whether the project is over or under budget.
Tip: earned value = the percent of work complete multiplied by your total budget (BAC).
The Cost Performance Index (CPI) is the core cost-efficiency measure in earned value management. It tells you how much budgeted work you are getting for every dollar you spend. A CPI of 1.0 means the project is exactly on budget; 0.90 means you're getting only 90 cents of planned work per dollar spent — a 10% overrun.
Where EV (earned value) is the budgeted cost of the work actually completed — percent complete multiplied by the budget at completion (BAC) — and AC (actual cost) is what you've spent to date.
| CPI | What it means |
|---|---|
| > 1.00 | Under budget — earning more work per dollar than planned |
| = 1.00 | Exactly on budget |
| 0.95 – 1.00 | Slight overrun — watch it |
| < 0.95 | Over budget — usually needs corrective action or a re-forecast |
Worked example: you've earned $1.85M of budgeted work and spent $1.9M. CPI = 1.85 / 1.9 = 0.97 — about 3% over budget, a cost variance of −$50k.
CPI drives the most common cost forecast: EAC = BAC / CPI. A CPI of 0.97 on a $4.2M budget forecasts completion at roughly $4.33M. That's why a small CPI slip matters — it scales across the whole remaining budget. Use the full earned value calculator to see EAC, SPI and TCPI together.
CPI (Cost Performance Index) is cost efficiency: EV / AC. 1.0 is on budget, above 1.0 is under budget, below 1.0 is over budget.
Divide earned value by actual cost: CPI = EV / AC. If you've earned $1.85M and spent $1.9M, CPI = 0.97.
1.0 or above is good. 0.95–1.0 is a mild overrun to watch; below 0.95 usually needs action or a re-forecast.
Aegis reads your schedule, tracks CPI and SPI over time, and flags the activities driving any overrun — no spreadsheets.
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