The formula
Sale price = original price − (original price × discount% ÷ 100). To reverse it: discount% = ((original − sale) ÷ original) × 100.
Worked examples
| Original price | Discount | You save | Sale price |
|---|---|---|---|
| $80 | 30% | $24.00 | $56.00 |
| $45 | 25% | $11.25 | $33.75 |
| $199 | 40% | $79.60 | $119.40 |
| $12.50 | 15% | $1.88 | $10.62 |
The stacking discounts trap
Two discounts don't simply add together — they multiply against the remaining balance. A common assumption is that "30% off" plus "an extra 20% off" equals 50% off the original price, but that's not how successive discounts work. Taking 20% off an already-discounted price means calculating 20% of the reduced amount, not the original.
For example: a $100 item with 30% off first becomes $70. An additional 20% off that $70 (not the original $100) brings it to $56 — a combined discount of 44%, not 50%. This is why "stacking" percentage discounts is always less generous than it sounds at first glance.
Discounts and sales tax
The order of operations matters here too. In most jurisdictions, sales tax is calculated on the discounted price, not the original price — so the discount should be applied first, and tax calculated on what's left. Applying tax first and then discounting the tax-inclusive total will usually produce a different (and incorrect) final number.
Frequently asked questions
How do you calculate a discounted price?
Multiply the original price by the discount percentage, then subtract that from the original price. 30% off $80 is $80 − ($80 × 0.30) = $56.
How do you calculate what percentage you saved?
Divide the amount saved by the original price, then multiply by 100.
Do two discounts add together?
No. A 30% discount followed by an additional 20% discount is not 50% off — the second discount applies to the already-reduced price, giving a combined discount of 44% in that example.
Understanding discounts
A discount reduces an original price by a percentage. The calculator shows both the amount saved and the resulting sale price, which makes it easier to check a shop's advertised percentage against the final number.
The basic formula
The discount amount is original price × discount rate ÷ 100. The sale price is original price minus that discount. For example, a 20% discount on $80 saves $16 and leaves a sale price of $64.
Stacked discounts
Two discounts applied one after another are not normally added together. A 20% discount followed by 10% off applies the second reduction to the already-discounted price. This is why a simple 30% assumption can be wrong.
Taxes and fees
A displayed sale price may not be the final amount paid. Sales tax, shipping, service charges or other fees can be applied separately. Use the calculator to check the discount itself, then review the seller's final checkout total.