If Actual is in A1, and budget in B1
The difference, how much actual exceeded budget, is (A1-B1)
Percentage is nothing more that a ratio, the difference compared to the
budget
is =(A1-B1)/B1
Generally these are small numbers and since most people are uncomfortable
with small numbers we used to multiply by 100 and call in percentage; in
worksheets we just format as percentage.
best wishes