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.
Nobody escalates a CPI of 0.97. It rounds to "about right", it survives a status meeting, and it compounds — on a $4.2M budget it is $130k gone if nothing changes, and nothing changes precisely because nobody escalated it.
By the time CPI is bad enough to force the conversation, the money is spent. The discipline that matters is not reading the index — it is deciding in advance which number triggers the meeting, and holding to that when the number arrives looking harmless.
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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