Percent Variance calculates the difference between two columns and divides by one of those columns (based on the report parameter order)

Note: In the examples below Column 3 is the actuals, and Column 4 is the budget.

Set up a new column with the following formula:

(Column 4 - Column 3)/Column 4

OR

GetPercentVariance({Column 3} , {Column 4})

Note: Column numbers used my vary depending on your report setup

If you want to get the opposite number
(Column 3 / Column 4)/100
For a budget of 500, and an actual of 200 this will show 40% instead of 60%.