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Cost Performance Index Calculator

Work out cost performance index instantly with clear inputs, formula shown and shareable results.

About Cost Performance Index Calculator

CPI is earned value over actual cost: below 1.0 means you are spending faster than you are earning. Dividing the budget by CPI gives an estimate at completion assuming current performance continues, and netting the remaining contingency against the projected overrun shows whether the project can still be delivered within its approved funding.

Formulas

Cost performance index

CPI = Earned value / Actual cost

Estimate at completion

EAC = Budget at completion / CPI

Overrun after contingency

Net overrun = (EAC - Budget at completion) - Contingency remaining

Worked example

With the default values below, Cost Performance Index Calculator returns Cost performance index of 0.9000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Earned value
10,080,000
Actual cost
11,200,000
Budget at completion
24,000,000
Contingency still available
1,200,000

Results

Cost performance index
0.9000
Estimate at completion
$26,666,666.67
To-complete performance index
1.0875
Overrun remaining after contingency
$1,466,666.67

Step by step

  1. 1Values used
  2. 2Cost performance index
  3. 3Estimate at completion
  4. 4Overrun after contingency
  5. 5Cost performance index= 0.9000
  6. 6Estimate at completion= 26,666,666.67
  7. 7To-complete performance index= 1.0875
  8. 8Overrun remaining after contingency= 1,466,666.67

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How reliable is CPI as a predictor?

Research on large projects shows cumulative CPI stabilises by around 20% completion and rarely improves after that, which makes early CPI a strong warning signal.

What TCPI is achievable?

Anything above about 1.10 is generally regarded as unrealistic. If TCPI exceeds that, the budget needs revising rather than the team exhorting.

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