The variance can either be caused by a difference in the fixed overheads at a given level of activity or because of a difference in the number of units produced (which affects the absorption of the overheads).
Because two different factors are affecting the total sales variance, they must be divided into the following 2 types (and the volume variance is also further subdivided as it is affected by 2 different factors):
Fixed Overhead Expenditure Variance
This is the difference between the actual and budgeted overheads.
Formula to calculate Fixed Overhead Expenditure Variance is
= Actual Overheads – Budgeted Overheads
Fixed Overhead Volume Variance
The fixed overhead volume variance is the difference between the budgeted fixed overhead and applied overheads. The volume variance measures the effect of the actual output departing from the output used at the beginning of the period to compute the predetermined standard fixed overhead rate.
The formula to calculate Fixed Overhead Volume Variance
= Standard Overhead Absorption Rate (OAR) x (Actual number of units – Budgeted number of units)
Fixed Overhead Efficiency Variance
This is the difference between the actual number of hours taken and the standard number of hours taken by the labour to produce the actual number of units.
Formula = Actual no. of labour hours – Standard Number of Labour Hours
Fixed Overhead Capacity Variance:
This is the difference between the actual number of hours worked and the standard number of hours worked by labour valued at the standard overhead absorption rate.
Formula to Calculate Fixed Overhead Capacity Variance = Standard Fixed Overhead Rate x (Actual Capacity Hours – Budgeted Capacity Hours)