How to Write Percentage Formulas in Excel

1. Calculate the percent of a total. Choose a cell for the percentage formula and enter the '=' symbol to activate the formula in Excel. Highlight the cell with the part, then enter the '/' symbol, and then select the cell with the total. For example, if the total lies in cell A10 and the part lies in A3, the formula is '=A3/A10'.
2. Calculate difference in percent between two numbers. Choose a cell for the percentage formula and enter the '=' symbol to activate the formula in Excel. Enter the opening parenthesis symbol, or '('. Highlight the cell with the first number, then enter the '-' symbol. Select the cell with the second number, and then enter the closing parenthesis symbol, or ')'. Then enter 'ABS' and select the second number to use its absolute value as a divisor. For example, if you are comparing sales data, and July 2011 sales are in A2 and the July 2012 are in B2, the formula is '=(B2-A2)/ABS(A2)'.
3. Select the percent cell and choose your format. From the Home tab, click 'Percent Style' from the Number group.