The one thing people get wrong about stacked discounts
Two 20%-off coupons do not add up to 40% off. Each discount applies to whatever price is left after the one before it, so the second discount is a smaller number of dollars than the first:
The gap between "36% actual" and "40% if you just added them" grows with more discounts stacked, which is exactly why store promotions that stack multiple coupons or sales still work out in the retailer's favor more often than shoppers expect.
The formulas
A full worked example
A $250 item with a 10% storewide sale, an additional 15% loyalty-member discount, and a 5% clearance tag, stacked in that order:
| Step | Price before | Discount | Amount off | Price after |
|---|---|---|---|---|
| 1 | $250.00 | 10% | $25.00 | $225.00 |
| 2 | $225.00 | 15% | $33.75 | $191.25 |
| 3 | $191.25 | 5% | $9.5625 | $181.69 |
Total saved: $68.31 — an equivalent single discount of 27.33%, not the 30% you'd get by adding 10 + 15 + 5.
Frequently asked questions
How is a discounted sale price calculated?
Amount off = original price × discount percent ÷ 100. Sale price = original price − amount off. An $80 item at 25% off saves $20 and sells for $60.
Do two stacked discounts add together?
No — this is the most common mistake with stacked discounts. Two 20% discounts do not combine to 40% off; each applies to the price left after the previous one, so they compound to 36% off, not 40%.
Does the order of stacked discounts change the result?
No — multiplying the same percentages together gives the same final price regardless of order. What matters is which discounts are eligible to stack at all, which is a store policy question, not a math one.
Should sales tax be calculated before or after the discount?
In virtually every real-world retail setting, tax is calculated on the discounted price — you're taxed on what you actually pay. This calculator applies tax after the discount (or after all stacked discounts) for that reason.
How do I find the original price if I only know the sale price and discount percent?
Original price = sale price ÷ (1 − discount percent ÷ 100). A $60 sale price at 25% off means the original price was $60 ÷ 0.75 = $80.
How do I find the discount percent if I only know the original and sale price?
Discount percent = (original − sale) ÷ original × 100. An $80 original and a $60 sale price gives (80 − 60) ÷ 80 × 100 = 25%.
What's the "equivalent single discount" shown for stacked discounts?
The one flat percentage that would produce the same final price as all the stacked discounts combined — shown next to the naive sum specifically to make the gap between them visible.