Stacked Discounts: 20% Off Plus 10% Off Is Not 30%
Learn why two percentage discounts do not add up, how to calculate the real total, and why dollar-off coupons change the answer depending on the order.
A sign says "20% off, plus an extra 10% off at checkout". Many shoppers expect 30% off, but the real discount is smaller, because the second discount applies to the price that is already lower.
Total discount = 1 − (1 − first discount) × (1 − second discount)
Example: 20% off, then 10% off $100
- After 20% off: 100 × 0.80 = $80
- After another 10% off: 80 × 0.90 = $72
You paid $72, so you saved $28. The total discount is 28%, not 30%.
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Common combinations
| First | Second | Real total discount |
|---|---|---|
| 10% | 10% | 19% |
| 20% | 10% | 28% |
| 30% | 20% | 44% |
| 40% | 10% | 46% |
| 50% | 20% | 60% |
| 25% | 25% | 43.75% |
Does the order matter?
For two percentage discounts, the order does not matter. 20% then 10% gives the same price as 10% then 20%.
For a dollar-off coupon combined with a percentage discount, the order does matter. On a $100 item with $10 off and 20% off:
- Coupon first, then percentage: (100 − 10) × 0.80 = $72
- Percentage first, then coupon: 100 × 0.80 − 10 = $70
Check the store's terms to see how your coupon is applied. Many stores apply the percentage discount to the original price first.
Add sales tax last
After all discounts, add sales tax to the final price. On the $72 example at 8% tax, the tax is $5.76, so the total is $77.76.
Use the calculator step by step
Run the first discount in the calculator, then enter the result as the new price and apply the second discount. That gives you the exact final price for any combination.
FAQ
Is 20% off plus 10% off the same as 30% off?
No. It is 28% off, because the second discount applies to the reduced price.
How do I calculate two discounts at once?
Multiply the two multipliers. For 20% and 10%, 0.80 × 0.90 = 0.72, so you pay 72% of the original price.
Which gives a bigger discount, 50% off or 30% plus 20% off?
50% off. Stacking 30% and 20% gives 44%.
Do dollar coupons stack the same way?
No, the order changes the result. See the $100 example above.