Percentage Decrease Calculator

Enter the original and new values to see the percentage decrease between them.

Understanding declines and discounts

Percentage decrease measures how much a value has fallen relative to its original level. Unless the value can go negative, the largest possible decrease is one hundred percent, which represents losing everything.

Decreases are not the mirror image of increases. Reversing a twenty percent discount does not mean adding twenty percent back, because the discount and the markup are taken from different bases. To undo a percent decrease you divide by one minus the rate.

This is the same arithmetic behind sale prices, depreciation, and any figure that shrinks over time, so the skill transfers well beyond shopping.

The formula

decrease % = ( (old - new) / |old| ) x 100

Worked example

From 80 to 60: ((80 - 60) / 80) x 100 = 25% decrease.

How to read your result

The tool reports the signed change; a negative percentage indicates the value dropped. The unit difference is shown below.

Frequently asked questions

Can a decrease exceed 100%?: Only if the new value is negative; otherwise the most you can lose is 100%.
What is the base for the percentage?: Always the original value before the change.
How do I reverse a discount?: To undo a percent decrease, divide by (1 - rate), not multiply by (1 + rate).

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