Project Budget Variance Calculator
Compute your project's Cost Variance (CV), Cost Performance Index (CPI), and Estimate at Completion (EAC) using Earned Value Management inputs. Use it during project execution to detect cost overruns before they become unrecoverable.
About this calculator
This calculator applies Earned Value Management (EVM) — a project-controls methodology that compares planned work, completed work, and actual spending. The primary output is Cost Variance: CV = Earned Value (EV) − Actual Cost (AC). A positive CV means you are under budget; negative means over. The Cost Performance Index, CPI = EV / AC, expresses how many dollars of value you are delivering per dollar spent — a CPI below 1.0 signals inefficiency. The Estimate at Completion (EAC) projects the final cost assuming current performance continues: EAC = Budget at Completion (BAC) / CPI. Together these metrics give project managers an objective, data-driven view of cost health at any point in the project lifecycle, replacing gut-feel assessments with quantifiable performance indices.
How to use
Assume BAC = $100,000, PV = $40,000, EV = $35,000, and AC = $42,000. Step 1 — Cost Variance: CV = EV − AC = $35,000 − $42,000 = −$7,000 (over budget). Step 2 — CPI: CPI = EV / AC = 35,000 / 42,000 ≈ 0.833 (earning only $0.83 per $1 spent). Step 3 — EAC: EAC = BAC / CPI = 100,000 / 0.833 ≈ $120,048. The project is forecast to overrun by roughly $20,000 if current spending efficiency continues, giving the PM time to intervene.
Frequently asked questions
What is the difference between Cost Variance and Schedule Variance in Earned Value Management?
Cost Variance (CV = EV − AC) measures whether you are spending more or less than the value of work completed, purely in dollar terms. Schedule Variance (SV = EV − PV) measures whether the value of completed work is ahead of or behind what was planned by this date, also in dollar terms. Both can be negative simultaneously — meaning you are behind schedule AND over budget — or they can diverge: you might be ahead of schedule but over budget because you added resources to accelerate delivery. Tracking both gives a two-dimensional view of project health.
How do I interpret a Cost Performance Index below 1.0 on my project?
A CPI below 1.0 means you are receiving less than one dollar of planned value for every dollar spent — the project is burning money faster than it is completing work. A CPI of 0.83, for example, means every $1.00 spent yields only $0.83 of earned value. Statistically, CPI tends to be stable after roughly 20% of project completion, meaning an early poor CPI is a reliable predictor of final cost. Project managers should investigate root causes — scope creep, estimation errors, or resource inefficiency — and consider re-baselining if the CPI drops below 0.9 consistently.
When should I use Estimate at Completion versus re-estimating from scratch?
EAC calculated from CPI (BAC / CPI) is most useful when you expect current inefficiencies to persist through project completion, providing a statistically grounded forecast without subjective re-estimation. It is the preferred approach when stakeholders need a quick, defensible number and when the project is more than 20% complete. A bottom-up re-estimate is preferable when a discrete, one-time event caused the variance (e.g., a vendor delay that has since been resolved) and future performance is expected to return to plan. Many organizations compute both and present the range as a forecast band.