Multiply the fraction by 100%. The fraction of interest is your grocery expense (230) divided by your total expense (2300).

230/2300*100% = 1/10*100% = 10%

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In Excel, if the grocery expense is in A1, and the total expense is in A2, the formula in A3 might be

230/2300*100% = 1/10*100% = 10%

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In Excel, if the grocery expense is in A1, and the total expense is in A2, the formula in A3 might be

**=A1/A2**Then cell A3 would be formatted to show numbers in % to as many decimal places as you might want.