Percentage Decrease Calculator

What this calculator does

You have a price and a discount, and you want the number at the till. A 100 jacket at 30% off, a rate cut by 12%, a value shrinking by a known percent. What is left after the reduction?

Type the original value and the percent to take off, and the tool gives you the new, smaller amount, along with how much came off.

Using the calculator

1. Type the original value.
2. Type the percentage to decrease by.
3. Press Calculate.

The percentage must be above zero. You get two numbers back: the decreased value, and the absolute difference, which is the amount that was taken off.

The formula | original − (original × percent) ÷ 100

The decreased value is:

original − (original × percent) ÷ 100

Work out the percentage of the original value, then take it away. The part being subtracted, (original × percent) ÷ 100, is the amount removed, which the tool also shows. The same calculation can be written as original × (1 − percent ÷ 100), multiplying the original by a single factor.

A worked example | 200 decreased by 25%

Say you start with 200 and decrease it by 25%.

1. The amount to remove: (200 × 25) ÷ 100 = 50.
2. Take it away: 200 − 50 = 150.

So 200 decreased by 25% is 150, with 50 taken off. If that 25% were a discount, 150 would be the sale price.

Applying a percent, or finding one

As with increases, there are two opposite questions. This tool applies a percentage you already know: "what is 200 reduced by 25%?" gives 150. The other direction finds the percentage from two values you already have: "a price fell from 200 to 120, what percent decrease is that?" For that, use the percent decrease calculator. One starts with a percent and produces a new value; the other starts with two values and produces a percent.

Why decreasing past 100% has no everyday meaning

Decreasing a value by 100% takes all of it away and leaves zero. You cannot really remove more than the whole of something, so a discount or reduction above 100% does not have a sensible meaning in everyday use. For real discounts, sales and reductions, the percentage you enter will sit between 0 and 100.

Questions people ask

What is 200 decreased by 25%?

150. Take 25% of 200, which is 50, off the 200.

What is the formula?

original − (original × percent) ÷ 100, which is the same as original × (1 − percent ÷ 100).

How is this different from the percent decrease calculator?

This one applies a percent you give to a value. The percent decrease calculator works the other way, finding the percent between two values you already have.

What is the absolute difference it shows?

The amount removed, (original × percent) ÷ 100. For 200 decreased by 25%, it is 50.

Can I decrease by more than 100%?

Not in any everyday sense. A 100% decrease leaves zero, and you cannot take away more than all of something, so real reductions stay between 0 and 100%.

References

A note on the idea behind it. Decreasing a value by a percentage takes that percentage of the value away, equivalent to multiplying by the factor 1 − percent ÷ 100. This is distinct from finding the percentage decrease between two known values. For further reading, see Relative change and difference.

1. Applying a percentage decrease, original × (1 − percent ÷ 100), to reduce a value by a known rate.