How a discount is calculated
A discount removes a share of the original price. "25% off" means you keep 75% of the price, so the arithmetic is a single multiplication rather than a subtraction:
sale price = original price × (1 − discount ÷ 100)
A €80 jacket at 25% off costs 80 × 0.75 = €60, and the amount saved is the €20 difference. Enter 80 as the base and −25 as the percentage above to see it worked through.
Working backwards from the sale price
If you know both prices and want the discount, switch to the percentage change mode:
discount = ((original − sale) ÷ original) × 100
A jacket reduced from €80 to €60 is a 25% discount. This is the useful direction when a shop advertises "was/now" prices without stating a percentage.
Stacked discounts and coupons
Discounts applied one after another multiply — they never simply add up. A 30% seasonal reduction followed by a 20% coupon leaves you paying 0.70 × 0.80 = 0.56 of the original, a 44% total discount rather than 50%.
| First discount | Second discount | You pay | True total discount |
|---|---|---|---|
| 10% | 10% | 81% | 19% |
| 20% | 10% | 72% | 28% |
| 30% | 20% | 56% | 44% |
| 50% | 20% | 40% | 60% |
| 50% | 50% | 25% | 75% |
The order of stacked discounts never changes the final price — multiplication is commutative. What does change it is whether tax is applied before or after the discount.
Frequently Asked Questions
- How do I calculate 20% off a price?
- Multiply the price by 0.80. A $45 item at 20% off costs 45 × 0.8 = $36, saving $9.
- How do I find the original price from a discounted price?
- Divide the sale price by 1 minus the discount. A $60 item after 25% off was 60 ÷ 0.75 = $80 originally.
- Do a 30% and a 20% discount make 50% off?
- No. They multiply to 0.7 × 0.8 = 0.56, which is 44% off in total.