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Microsoft Excel handles a large variety of mathematical functions through the use of formulas. Formulas can be designed to calculate many different values, from simple sums to complex statistical analysis, using the data in the spreadsheet. The mathematical formula for calculating percentages is the amount divided by the total. This formula is easy to translate into Microsoft Excel, where it can be used in a variety of applications, such as calculating sales taxes and test scores.

Calculate the per cent 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".

Calculate difference in per cent 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)".

Select the per cent cell and choose your format. From the Home tab, click "Percent Style" from the Number group.

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- If you are completing a one-time calculation, write the formula as an absolute reference. To do so, put a "$" symbol in front of every row and column reference. For example, you type "=$A$3/$A$10" to always reference the data in those cells.

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