Percentage Decrease Calculator

This page opens with Calculate on Decrease Y by X%, so the two boxes are all you need.

1. Type the amount to take off in Percent to subtract (X). It begins at 20.
2. Type the number you are reducing in Starting number (Y). It begins at 150.
3. Read the large result: 150 decreased by 20.00% is 120, and the line under it says that this removes 30.
4. Check the formula line, which fills in your numbers: 150 x (1 - 20.00 / 100) = 120.
5. If you already know both prices and want the discount rate, switch Calculate to Percentage change from X to Y.

In that second mode the boxes keep their labels. Type the old value into the first one and the new value into the second, and expect a result such as Decrease of 20.00% for 150 and 120.

Taking a percent off is the same as multiplying by one minus the rate. A 20 percent reduction keeps 80 percent of the price, so the multiplier is 0.8 and 150 x 0.8 = 120. A shop might mark a coat of 1,200 down by 15 percent. Multiply by 0.85 and the price is 1,020, which removes 180.

Depreciation works the same way, repeated. Suppose a vehicle worth 24,000 loses 15 percent of its value each year. The percentage is taken from what is left, not from the original price:

To follow a third year, enter 17,340 as the starting number again. Each year removes a little less money than the one before, even though the rate is constant. Real depreciation is rarely this steady, so treat a figure like this as a rough illustration.

Budgets follow the same rule. If a team of 40 hours a week is cut by 12.5 percent, it keeps 87.5 percent of its time, which is 35 hours and removes 5. Enter 12.5 and 40 to see it. Because the result is the starting number times a multiplier below 1, it is always smaller than Y when the rate is positive and under 100.

Two reductions in a row never add up to their sum. Take an item priced at 80, with 25 percent off and then a further 10 percent off the reduced price. The first step gives 60 and the second gives 54. The total reduction is 26 on 80, which is 32.5 percent, not 35. A flat 35 percent off would have left 52. For several discounts at once, see the discount calculator.

A common slip goes the other way. A jacket costs 120 after 20 percent off, and you want the original price. Adding 20 percent back, 120 x 1.20 = 144, is wrong. The sale price is 80 percent of the original, so divide: 120 / 0.8 = 150. A plain division on a scientific calculator does this in one line, and the decrease preset then confirms it, since 150 less 20 percent is 120.

Going the other direction, to add a rate rather than remove one, use the percentage increase calculator.

The tool removes one rate from one number. It does not round to cents, so a money result such as 86.625 needs rounding by you. It also does not stop you from entering a rate above 100: taking 120 percent off 150 returns -30 without a warning. A negative answer usually means the rate was mistyped.

If you have both prices and want the size of the move, the percent change calculator is set up for that. The general version with all five modes is the percentage calculator. Weight changes, savings targets and budget cuts can all be checked here as plain arithmetic, but the results are for general information and not medical or financial advice.