Cost Performance Index (CPI)
Earned value relative to actual cost for project budget efficiency
FORMULA
CPI = Earned Value (EV) / Actual Cost (AC)
Alternate Calculations
Cost Variance
EV - AC (in dollars)What is Cost Performance Index?
Cost Performance Index measures project budget efficiency by comparing Earned Value to Actual Cost. CPI = EV / AC. Critical for construction cost control.
CPI > 1.0 indicates under budget; CPI < 1.0 indicates over budget. Used to forecast project profitability and identify cost overrun risk.
Chart
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Sample Data
| week | ev | ac | cpi | margin |
|---|---|---|---|---|
| 1 | 95,000 | 98,000 | 0.969 | -3% |
| 2 | 205,000 | 202,000 | 1.015 | +1.5% |
| 3 | 315,000 | 310,000 | 1.016 | +1.6% |
| 4 | 420,000 | 413,000 | 1.017 | +1.7% |
Required Data Columns
earned_valueactual_costcpi