Everyday · 4 min read

How to Calculate a Discount Percentage

Written by Muhammad Ajmal · Last reviewed 2026-08-02

Calculating a discount percentage comes up constantly, whether you're checking a sale tag at a store or figuring out how much a coupon actually saves. Our discount calculator does the math instantly once you enter the original price and the discount rate, but knowing the formula yourself makes it easy to double-check a receipt or compare two different sales.

The basic formula

To find the sale price, multiply the original price by the discount percentage, then subtract that amount from the original price. Written as a formula: sale price equals original price minus (original price times discount rate). A faster version of the same calculation is to multiply the original price by one minus the discount rate as a decimal, which gives you the sale price in a single step.

A worked example

Say a jacket costs 80 dollars and is marked 25 percent off. Convert 25 percent to a decimal, which is 0.25, then multiply that by 80 to get 20 dollars. That 20 dollars is the amount you save, so subtract it from the original price: 80 minus 20 leaves a sale price of 60 dollars. Using the one-step version, 80 times (1 minus 0.25), or 80 times 0.75, gives the same result of 60 dollars directly.

Finding the discount percentage from two prices

Sometimes you know the original price and the sale price but not the discount rate itself, such as when comparing store markdowns. Subtract the sale price from the original price to find the amount saved, divide that by the original price, then multiply by 100 to get a percentage. For a shirt that dropped from 40 dollars to 30 dollars, the amount saved is 10 dollars. Dividing 10 by 40 gives 0.25, and multiplying by 100 shows the shirt was discounted 25 percent.

How stacked discounts actually work

A common mistake is adding two discounts together, but percentages off a price don't stack that way. If an item is 20 percent off and you have an additional 10 percent off coupon, the second discount applies to the already-reduced price, not the original one. A 100 dollar item at 20 percent off becomes 80 dollars, and then 10 percent off that 80 dollars is 8 dollars, bringing the final price to 72 dollars. That's different from a flat 30 percent off 100 dollars, which would come to 70 dollars. Stacked percentage discounts are always a little less generous than adding the percentages suggests.

Discounts and sales tax

Order of operations also matters when tax applies. Discounts are almost always calculated on the original price first, with sales tax then applied to the reduced price, not the other way around. Using the earlier jacket example, if the 60 dollar sale price is taxed at 8 percent, the tax adds 4.80 dollars, for a final total of 64.80 dollars. Applying tax to the original 80 dollar price and then discounting the total would produce a different, incorrect number.

Quick mental math shortcuts

For common round percentages, mental shortcuts can save time without a calculator. Finding 10 percent of a price just means moving the decimal point one place to the left, so 10 percent of 80 dollars is 8 dollars. Once you have 10 percent, 20 percent is double that, 5 percent is half of it, and 25 percent is a quarter of the original price. Combining these building blocks covers most sale percentages you'll run into while shopping.

Frequently asked questions