Project Cost Variance Calculator
Cost variance is the heart of earned value management's budget control. Instead of comparing spend to a calendar plan, it compares the value of work actually completed against what that work cost, so it tells you whether you are getting your money's worth. The companion cost performance index turns the same comparison into a ratio you can track and forecast with. Enter the earned value (budgeted cost of completed work), the actual cost incurred, and the total budget at completion, and this calculator returns the cost variance, the cost performance index, and a forecast estimate at completion.
Cost variance formula
Cost variance = EV - AC
Cost performance index = EV / AC
Estimate at completion = BAC / CPI
A positive cost variance and a CPI above 1.0 mean the project is under budget. The estimate at completion projects the final cost if current cost efficiency continues.
Reading the results
- CV greater than zero and CPI greater than 1.0: under budget for work performed.
- CV less than zero and CPI less than 1.0: over budget for work performed.
- CPI of 0.89 means you receive 89 cents of value per dollar spent.
- The estimate at completion warns early when overruns are likely.
- Pair cost variance with schedule variance for the full earned value picture.
Project cost variance: frequently asked questions
What is cost variance in project management?
Cost variance (CV) is an earned value management metric that compares the budgeted value of work completed against what was actually spent. It equals earned value minus actual cost. A positive CV means the project is under budget for the work done; a negative CV means it is over budget.
How is cost variance calculated?
Cost variance equals earned value (EV) minus actual cost (AC). Earned value is the budgeted cost of the work that has actually been completed, and actual cost is the money spent to complete it. For example, EV of US$80,000 and AC of US$90,000 gives a cost variance of negative US$10,000.
What is the cost performance index?
The cost performance index (CPI) is earned value divided by actual cost. A CPI of 1.0 means the project is exactly on budget, above 1.0 means under budget, and below 1.0 means over budget. A CPI of 0.89, for instance, means you are getting 89 cents of value for each dollar spent.
What is the difference between cost variance and schedule variance?
Cost variance compares earned value to actual cost and measures budget performance. Schedule variance compares earned value to planned value and measures timing performance. Together they form the core of earned value management, showing whether a project is on budget and on schedule.
How do I estimate the final cost from CPI?
A common forecast is the estimate at completion, which equals the budget at completion divided by the CPI, assuming current cost efficiency continues. This calculator computes that estimate so you can project the likely final cost from current performance.
Official sources
- U.S. Government Accountability Office: Cost Estimating and Assessment Guide.
- U.S. Small Business Administration: Manage your finances.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.