CPI Calculator (Cost Performance Index)

Q: What is CPI (Cost Performance Index)?

CPI = Earned Value / Actual Cost. CPI > 1 means Under budget.

PercentageCalculatorFree.com Team Last Updated: January 20, 2026

Measure how efficiently your project team is using time compared to the plan.

CPI Score

Understanding Schedule Performance Index

What is CPI?

Cost Performance Index (CPI) measures project schedule efficiency. Its the ratio of earned value to Actual Cost - telling you if you are on track.

CPI > 1.0: Under budget
CPI = 1.0: Exactly on budget
CPI < 1.0: Over budget

The Formula

CPI Calculation

CPI = Earned Value (EV) / Actual Cost (AC)

Worked Example

Scenario: Work worth $80,000 completed, but actual costs were $100,000.

Step 1: Earned Value = $80,000

Step 2: Actual Cost = $100,000

Step 3: SPI = 80000 / 100000 = 0.80

SPI = 0.85 - 15% Over budget

Common Use Cases

Project status: Monthly progress reporting
Forecasting: Estimate project completion date
Recovery: Determine if crash or fast-tracking needed

Pro Tips

Use with SPI: Together they show cost and schedule health
Early warning: CPI rarely recovers once it drops below 0.9
Weekly tracking: Catch slippage early

CPI: The Ultimate Budget Health Metric

Cost Performance Index measures how efficiently you're converting project budget into actual deliverables. A CPI of 1.0 means you're getting exactly one dollar of value for every dollar spent. Higher is better.

CPI Interpretation Guide

CPI > 1.0: Under budget - getting more value than planned per dollar
CPI = 1.0: Exactly on budget - perfect cost efficiency
CPI = 0.8: 25% over budget - only getting 80 cents of value per dollar
CPI < 0.9: Red flag - requires immediate corrective action

The CPI Recovery Myth

Research from thousands of government and private sector projects shows a critical insight: CPI rarely improves once established. If your project has a CPI of 0.85 at 20% complete, expect a final CPI around 0.85. This means early detection is everything.

❓ Frequently Asked Questions

What is CPI (Cost Performance Index)?

CPI = Earned Value / Actual Cost. CPI > 1 means Under budget.

How do I interpret CPI values?

CPI = 1.0: On budget. CPI = 1.2: 20% under budget. CPI = 0.8: 20% over budget.

Can I use CPI to forecast final project cost?

Yes: EAC (Estimate at Completion) = BAC / CPI.

🔍 Authoritative References

For more information about professional and project management calculations, consult these trusted sources:

Project Management Institute - Project management standards and best practices
OSHA - Workplace safety standards and guidelines
ISO Standards - International quality and process standards