The per cent gain or loss is used to compare changes over time of different scales. By using percentages rather than raw numbers, you can accurately compare different sizes, such as an investment of £65 and an investment of £6,500. Though you could calculate the per cent change with a calculator, using a spreadsheet program, such as Microsoft Excel, allows you to change the numbers that you use to quickly see how the per cent change would be altered.

Label cell A1 "Original Value," cell A2 "Final Value" and cell A3 "Percent Change."

Enter the original value in cell B1 and the final value in cell B2. For example, if the original value equals 71 and the final value equals 80, you would enter 71 in B1 and 80 in B2.

Enter the formula "(B2-B1)/B1*100" and Excel will display the gain or loss expressed as a percentage. In the example, when you enter the formula, Excel displays "12.67605634" meaning you have a 12.67 per cent increase.