Microsoft Excel spreadsheets can handle inventory: what you have, what you had, what you sold and what you have left. You can input figures into a Microsoft Excel spreadsheet and subtract a number from what you originally had in inventory to determine what's left. You can use negative numbers to show the difference; for example with "15 - 10," this equation is actually “15 + (-10).”

You can format the way negative numbers appear in your spreadsheet. Numbers can be formatted with a negative sign, with double parentheses, or by using the color red.

## Calculating Negative Numbers

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Enter a negative number into an Excel spreadsheet cell by using the minus sign (-) before the number.

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“-12” is an example of a negative number.

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Use the arithmetic operator, the minus sign (-), to subtract a number using a formula.

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An example is the formula, “=25-10” that will give a result of “15.”

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Use a function to calculate negative and positive numbers.

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An example of this is “=sum(a1:a3)”, where cell a1=10, cell a2=12 and cell a3=-25 will give a result of “-3.”

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Use a function to transform a positive result into a negative result by applying the negative sign (-) to the function. An example of this is “=-sum(a1:a3)” using the established values for those cells will give a result of “3.”

## Change Negative Number Formats

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Select a number or range of numbers to change the way Excel displays these numbers.

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Click the “Home” tab on the top menu and select the arrow in the “Number” section.

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Choose either the “Number” or the “Currency” category in the “Category:” list in the “Format Cells” window.

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Select the number of decimal places by either typing it in or selecting the up or down arrow in the "Format Cells" window.

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Choose the “Use 1000 Separator (,)” check box. Skip this if you are formatting currency.

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Choose the currency symbol by clicking the down arrow in the box next to “Symbol.” Skip this if you are not formatting currency.

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Select the number format in the “Negative numbers:” box in the “Format Cells” window.

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Click the “OK” button.