Discount Calculator
Sale tags are designed to confuse: “30% off plus an extra 20% off” is not 50% off. This discount calculator applies one or two stacked discounts to any price and shows the final price, total savings and the true effective discount.
Use it in the store, during Black Friday, or when setting sale prices for your own products.
Enter valid values to see the results.
Formula
Stacked discounts multiply, they do not add: 30% + 20% off leaves 0.70 × 0.80 = 0.56 of the price — an effective discount of 44%, not 50%. The second discount always applies to the already-reduced price.
What you need
- Original price: the price before any discount (the crossed-out tag price).
- Discount: the first percentage off. Extra discount: an optional second discount applied on top, common in clearance sales.
- Leave the extra discount at 0 for a simple single-discount calculation.
Worked example
Practical tips
- Compare effective discounts, not headline numbers: 40% off beats 25% + 15% (which is only 36.25%).
- A “50% off the second item” deal on two equal items is really 25% off the pair.
- To reverse-engineer the original price from a sale price, divide by (1 − discount): $140 ÷ 0.56 = $250.
- Check the unit price too — sometimes a bigger pack with a smaller discount is still cheaper per unit.
Effective discount of stacked offers
| First | Second | Effective | Pays |
|---|---|---|---|
| 10% | 10% | 19% | 81% |
| 20% | 10% | 28% | 72% |
| 30% | 20% | 44% | 56% |
| 50% | 25% | 62.5% | 37.5% |
Common mistakes
- 1 Adding stacked discounts (30% + 20% ≠ 50%) — the second cut applies to the reduced price.
- 2 Forgetting tax: in many regions sales tax or VAT is applied to the discounted price, changing the checkout total.
- 3 Anchoring on the crossed-out price, which some sellers inflate before the sale.
Frequently asked questions
How do I calculate 20% off a price?
Multiply the price by 0.80. For $90: 90 × 0.8 = $72. The saving is the price × 0.20 = $18.
Is 30% + 20% off the same as 50% off?
No. Stacked discounts multiply: 0.70 × 0.80 = 0.56, so you pay 56% of the original — an effective 44% discount. A straight 50% off is better.
How do I find the original price before a discount?
Divide the sale price by (1 − discount). If an item costs $60 after 25% off: 60 ÷ 0.75 = $80.
What does “up to 70% off” usually mean?
That a few items are 70% off while most are discounted far less. Always compute the actual discount on the specific item you want.