Percentage CalculatorYTScript

Percentage Decrease Calculator

See how much a number fell, or what remains after reducing a value by a percent.

Runs in your browser — numbers never leave this device

Enter two numbers

Pick a question and fill both fields — the answer appears as you type.

How to use it

  1. 1

    Choose “from one number to another” or “decrease a number by a percent.”

  2. 2

    Enter the values. The result is named as a decrease or an increase, not just a sign.

  3. 3

    If you wanted a directionless difference instead, use the comparison and the link on the result.

A decrease uses the starting point as the base

The formula is the same as on the increase page: (new − old) / |old| × 100. From 200 to 100 is a decrease of 50%. The reverse trip, 100 to 200, is an increase of 100%. Those two figures are not interchangeable, and neither one is the percentage difference of the same pair (66.67%).

Reducing a number by P% uses starting value × (1 − P/100). A 100% decrease is 0. A decrease of more than 100% goes negative; that is a mathematical result, not a second kind of error. A change that starts at zero is not defined.

Other percentage tools

Percentage calculatorFind a percent of a number, or what percent one number is of another.Percentage increaseHow much a number rose, or add a percent to a value.Percentage differenceHow far two numbers sit from their average.DiscountSale price, amount saved, or the original price.TipTip amount, total to pay, and an optional split.Test scoreTurn points scored and a total into a percentage.FractionConvert fractions, decimals, and percentages.

Frequently asked questions

What is the formula for a percentage decrease?

It is the same change formula as an increase: (new − old) / |old| × 100. When the new value is smaller, the result is reported as a decrease.

How do I take 25% off a number?

Use the second option. 80 decreased by 25% is 80 × (1 − 0.25) = 60. Increasing 80 by −25% gives the same 60.

What happens if I decrease by more than 100%?

The result is negative. The page still shows it and notes that this is the mathematical result.

Why is a drop from 120 to 100 not 20%?

20 is 16.67% of 120, not 20% of 120. A 20% decrease would land on 96. The 20% figure people sometimes expect is the increase from 100 to 120, which uses a different base.

Where is percentage difference?

On its own page. Difference uses the average as the base and does not depend on order. This result card always shows that other number too.