How to Calculate a Discount (And Check a Store Isn't Overcharging You)

“25% off” sounds simple, but two situations trip people up constantly: figuring out the exact final price before checkout, and stacking multiple discounts correctly. Here’s the math for both.

The basic formula

amount saved = original price × (discount percent ÷ 100)
final price  = original price − amount saved

A $80 jacket at 25% off:

amount saved = 80 × (25 ÷ 100) = $20
final price  = 80 − 20 = $60

Stacked discounts don’t add up the way you’d expect

If a store advertises “25% off, plus an extra 10% off,” it is not a 35% discount. Each discount applies to the already-discounted price, one after another:

step 1: $80 × (1 − 0.25) = $60
step 2: $60 × (1 − 0.10) = $54

$54 is a 32.5% total discount — noticeably less generous than 35% would be. This is worth checking any time you see “stacked” or “additional” discounts advertised.

Working backward from a sale price

Sometimes you know the sale price and the discount percentage, and want the original price. Rearranging the formula:

original price = final price ÷ (1 − discount percent ÷ 100)

A $60 item marked “25% off” started at 60 ÷ 0.75 = $80.

Try it yourself

The percentage calculator’s Discount tab computes the amount saved and final price instantly as you type — and the Reverse % tab handles the “what was the original price” direction, all processed locally in your browser.