Variable expenses

Apart from prime costs which are variable, the overhead expensesthat change in proportion to the change in the level of activity are also variable expenses.
Thus when expenses go up or come down in proportion to a change in the volume of
output, such that, with every increase of 20% in output, expenses also go up by 20% or
vice versa, these expenses are known as variable expenses. Variable expenses fluctuate
in total with fluctuations in the level of output but tend to remain constant per unit of
output. Examples of such expenses are raw material, power, commission paid to
salesmen as a percentage of sales, etc.