Math CentralQuandaries & Queries


I need a formula for calculating percentages in Excel. For example, we sold 4 units of an item one month, and 105 units the next. I need a formula to calculate the percentage increase in sales units. Also, if 5251 were sold one month and 651 the next, what is the formula for calculating the percentage difference? Please help, thank you.

Hi Karen,

If you sold 50 items one month and 70 the next month then the percentage change is

(70 - 50)/50 × 100 = 40%

Since this is positive there is a 40% increase.

If, as in your second example the sales go from 5251 to 651 then the percentage change is

(651 - 5251)/5251 × 100 = -87.6%

Since this number is negative there is an 87.6% decrease.

If a quantity starts at some level a and changes to a second level b then the percentage change is

(b - a)/a × 100


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