CV (Cost Variance)
Cost Variance (CV) is earned value (EV) minus actual cost (AC). Negative CV means spend is outrunning completed value — the project is overrunning its budget.
How it is computed
CV = EV − AC: earned value minus actual cost. If $40k of value is complete but $48k has actually been spent, CV is −$8k — the spend is outrunning the completed value. Zero means on budget, negative means overrun, positive means the money is buying more value than planned. As a ratio, use the Cost Performance Index, CPI = EV ÷ AC — about 0.83 in the example.
Why it matters
A spend report alone cannot show an overrun. "60% of budget consumed" is only reassuring when 60% of the work is done. CV pairs the money spent with the value completed, so even a modest burn rate turns negative the moment completion lags spend. And a cost overrun is famously harder to recover than a schedule slip — the earlier CV turns negative, the more options remain.
Common misconceptions
CV and SV are often read as the same kind of signal. They are different axes: SV (schedule variance) compares progress against the plan, CV compares completion against spend, and a project can be ahead of schedule while over budget. CV is also not an accounting total. Unless what counts into AC and how EV is measured are agreed first, every team computes a different CV. Agreement on measurement comes before the formula.
wbsgantt's simplified EVM takes no cost input and does not provide CV; the schedule axis ships as SPI and SV, with cost EVM on the roadmap.