Decrease a number by a percentage. Enter the starting value and the percent to remove.
Usage Tip
To subtract a percent fast, multiply by 1 minus the decimal: minus 20% is times 0.8, minus 25% is times 0.75. A 50% off then another 50% off is 75% off total, not 100%.
Result = value − decrease
A decrease cannot exceed 100% of the value (which would reach zero); beyond that the result goes negative.
Successive decreases compound on the shrinking total, so two 10% cuts is a 19% drop, not 20%.
A decrease does not undo an equal-percent increase — up 25% then down 25% lands below the original.
To decrease a number by a percentage, multiply it by one minus the percentage written as a decimal. Reducing 80 by 25 percent gives 80 times 0.75, which is 60. This is the calculation behind sale prices, discounts, and reductions in quantities or budgets.
A percentage decrease and a percentage increase are not exact opposites. If a price falls by 20 percent and then rises by 20 percent, it ends up 4 percent lower than where it began, because the second change applies to a smaller number. To undo a decrease, you need a larger percentage increase, so a 50 percent drop needs a 100 percent rise to return to the start.