In budgeting (or management accounting in general), a variance is the difference between a budgeted, planned or standard cost and the actual amount incurred/sold. Variances can be computed for both costs and revenues. This equation shows the percentage of variance in relation to expense.
Resource:
Dopson, Lea R., and David K. Hayes. Managerial Accounting for the Hospitality Industry. Hoboken, NJ: Wiley, 2009. Print.