CPI Calculator

Q: What is CPI (Cost Performance Index)?

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

Written by Priya Nair, Senior Content Editor Reviewed by Vikram Sen, Technical Reviewer Last updated: June 1, 2026 Last verified: June 1, 2026 · Methodology · Accuracy policy

Cost Performance Index compares earned value to actual cost—above 100% means more value than spend so far.

CPI % = (earned value ÷ actual cost) × 100.

Tip: Keep EV and AC on the same currency and reporting date; mixing baselines invents fake efficiency.

Cluster: Professional KPI hub · Complete percentage guide

Cost performance index (CPI) from earned value and actual cost. CPI compares the budgeted value of finished work to what you actually spent to produce it. Values above 1 mean you are delivering more value per dollar than planned; below 1 signals overspending for the progress earned.

This is cost-only—use SPI for schedule pace (EV vs planned value) and cost variance for the percent gap versus AC.

Provide earned value and actual cost below.

CPI Score

CPI: The Ultimate Budget Health Metric

Cost Performance Index (CPI) is EV÷AC efficiency—not SPI. Use the SPI calculator for schedule efficiency. 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.

Cpi — understanding Cost Performance Index

How we calculate. CPI = earned value ÷ actual cost (shown as a percent × 100 in the result). Values above 100% mean under budget for earned work. See our methodology and accuracy policy .

Real-world scenario: A PM compared $9,000 earned value to $10,000 actual cost (CPI 0.90 / 90%) and flagged the overrun in the weekly status report.

What is CPI?

Cost Performance Index (CPI) measures project cost efficiency. It is the ratio of earned value to actual cost—telling you whether you are under or over budget.

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: CPI = 80000 / 100000 = 0.80

Answer: 80% (part ÷ whole × 100; verified with this calculator).

Common Use Cases

Project status: Monthly earned-value reporting
Forecasting: Estimate cost at completion (EAC)
Recovery: Decide when cost corrective action is required

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 overruns before they compound

Common CPI mistakes

Confusing CPI with SPI: CPI uses Actual Cost (AC); SPI uses Planned Value (PV).
Stale earned value: EV must reflect work actually completed, not invoices submitted.
Ignoring trend: A single CPI snapshot is less useful than the trend over reporting periods.

Limitations: cpi calculator results are estimates for learning and quick checks—not financial, legal, tax, or medical advice. Policies, grading scales, and local rules may differ; confirm outcomes with official sources before making decisions.

When to use this calculator

Use this page when you need Cost Performance Index from EV and AC.
Use cost variance for the dollar/percent variance framing.
Use SPI for schedule performance instead of cost.

Still unsure about cpi? Start with the quick answer above, then open the linked calculator that matches your wording.

Comparison: when to use each method

Use this table to pick the right percent workflow before you calculate.

Scenario	When to use
Percent of a number	Finding a part of a whole (tax, tip, score)
Percent change	Comparing old vs new values

❓ 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