Discount Calculator
Your details
Advanced options
Result
Answer
- You save
- $24.00
- Effective discount
- 30.00%
- Working
- 80 × 0.7 = 56
This price at common discounts
| Discount | Sale price | You save |
|---|---|---|
| 10% | $72.00 | $8.00 |
| 15% | $68.00 | $12.00 |
| 20% | $64.00 | $16.00 |
| 25% | $60.00 | $20.00 |
| 30% | $56.00 | $24.00 |
| 40% | $48.00 | $32.00 |
| 50% | $40.00 | $40.00 |
| 60% | $32.00 | $48.00 |
| 70% | $24.00 | $56.00 |
How do you calculate a discount?
To calculate a discount, multiply the original price by the discount percentage to find the saving, then subtract it. For 30% off $80: 0.30 × 80 = $24 saved, leaving $56. Multiplying by 0.70 directly gives the same sale price in one step.
sale price = original × (1 − d) stacked = original × (1 − d₁) × (1 − d₂) original = paid ÷ (1 − d)- original
- The price before any discount
- d
- The discount as a decimal — 30% is 0.30
- d₁, d₂
- First and second discounts, applied in sequence
A single discount is one multiplication: multiply by one minus the rate and you have the sale price directly, without the intermediate step of working out the saving. Stacked discounts are where this gets interesting, and where retailers and shoppers both go wrong. Taking 30% off and then a further 20% off is not 50% off. The second discount applies to the already-reduced price, so the combined effect is 1 − (0.70 × 0.80) = 44%. The gap widens with larger discounts: 50% then 50% is 75% off, not 100%. Reversing a discount is a division rather than an addition, which is the most common error in this family. An item that cost $56 after 30% off was originally $56 ÷ 0.70 = $80, not $56 + 30% = $72.80. Sales tax, where it applies, is charged on the discounted price, so a discount reduces the tax owed as well as the price.
- Convert the discount percentage to a decimal by dividing by 100.
- Subtract that from one to get the fraction you still pay.
- Multiply the original price by that fraction for the sale price.
- For a second discount, multiply again by one minus its rate.
- To reverse a discount, divide the paid price by that same fraction.
Worked example: An $80 item at 30% off, then a further 20% coupon
An $80 item at 30% off, then a further 20% coupon
The first discount takes 30% off $80. Multiplying by 0.70 gives $56, so the saving is $24. The coupon then takes 20% off that $56 rather than off the original $80 — multiplying by 0.80 gives $44.80. Total saved is $35.20, which is 44% of the original price, not the 50% that adding 30% and 20% would suggest. That six-point gap is the whole point: stacked discounts compound, and the order does not matter — 20% then 30% also lands on $44.80. Working backwards confirms it: $44.80 ÷ 0.80 ÷ 0.70 = $80. And note what reversing a single discount looks like — the $56 after 30% off recovers to $56 ÷ 0.70 = $80, whereas adding 30% back to $56 would give $72.80, which is wrong by $7.20.
What each discount input means
- What do you want to work out?
- Pick the question. The inputs below change meaning to match.
- Original price
- The price before discount. In reverse mode, enter the price you actually paid here instead.
- First discount
- The percentage off. In reverse mode, the discount that was applied.
- Additional discount
- A second discount applied after the first — a coupon on top of a sale. These compound rather than add, which is the point of this field.
- Price you paid
- Used when working out the discount percentage from two known prices.
- Sales tax
- Applied to the discounted price, since tax is charged on what you actually pay.
What this discount does not account for
- Stacked discounts compound rather than add. 30% then 20% is 44% off, not 50%, because the second applies to the reduced price. The gap widens as the discounts get larger.
- Reversing a discount is a division, not an addition. Adding the percentage back to the sale price always understates the original.
- The order of stacked discounts does not change the result, since multiplication commutes — though a retailer's terms may dictate an order anyway.
- Sales tax is charged on the discounted price in US practice, so a discount reduces the tax owed too. Some jurisdictions treat manufacturer coupons differently from store discounts.
- A "buy one get one free" offer is a 50% discount across two items, not 100% off one. "Buy two get one free" is 33.3% off.
- Advertised "up to" discounts apply only to selected items, and a percentage off an inflated reference price is not a real saving of that size.
Frequently asked questions
How do you calculate 30% off?
Multiply the price by 0.70, which is one minus 0.30. For an $80 item that is $56. Alternatively, multiply by 0.30 to get the $24 saving and subtract it — the same answer in two steps.
Do stacked discounts add together?
No, they compound. 30% off followed by 20% off is 44% off in total, not 50%, because the second discount applies to the already-reduced price. Larger discounts widen the gap further.
How do you find the original price from a sale price?
Divide by one minus the discount rate. An item costing $56 after 30% off was $56 ÷ 0.70 = $80. Adding 30% back to $56 gives $72.80, which is wrong.
How do you work out what percentage off something is?
Subtract the sale price from the original, divide by the original, and multiply by 100. From $80 to $56 is a $24 saving, and 24 ÷ 80 × 100 = 30% off.
Is sales tax charged before or after a discount?
After, in US practice — tax applies to what you actually pay. So a discount reduces the tax owed as well as the price. Manufacturer coupons are sometimes treated differently from store discounts.
What percentage is buy one get one free?
Fifty percent, spread across the two items — not 100% off one. Buy two get one free is 33.3% off, and buy three get one free is 25% off.
Sources and review
Last reviewed .