The cost variance formula is defined as the ‘difference between earned value and actual costs. (CV = EV – AC)’ (PMI, 2004, p. 357) Sometimes this formula is expressed as the difference between budgeted cost of work performed and actual cost work performed. If the variance is equal to 0, the project is on budget. If a negative variance is determined, the project is over budget and if the variance is positive the project is under budget.