Discount Calculator (Sale Price & Stacked Discounts)
Enter the original price and the discount — plus an optional second "extra % off" coupon and sales tax. See the real final price and exactly how much you save.
| You save | — |
| Effective total discount | — |
| Price before tax | — |
How discounts are calculated
Sale price = Original × (1 − Discount ÷ 100)
30% off $120 takes off $36, leaving $84. Simple — until stores stack discounts.
The stacked discount trick
"30% off, plus an extra 20% off" is not 50% off. The second discount applies to the already-reduced price:
- $120 − 30% = $84
- $84 − 20% = $67.20
- Effective discount: 44%, not 50%
Retailers advertise stacked percentages precisely because shoppers add them in their heads. The calculator shows the true effective discount so you can compare deals honestly.
Quick mental math for percent off
- 10% off: move the decimal — $47.00 → $4.70 off.
- 20% off: double the 10% figure.
- 25% off: quarter the price and subtract it.
- 30% off: triple the 10% figure.
Frequently asked questions
What is 30% off $120?
30% off $120 is a $36 discount, making the sale price $84.
Is 30% off plus an extra 20% off the same as 50% off?
No. The extra 20% applies to the already-discounted price: $120 becomes $84, then $67.20 — an effective 44% discount, not 50% ($60).
How do I calculate a discount without a calculator?
Find 10% by moving the decimal point one place left, then scale: 30% is three times the 10% amount. For $85, 10% is $8.50, so 30% off is $25.50 off, leaving $59.50.
Is sales tax charged on the original or discounted price?
In the US, tax applies to the price actually paid — the discounted price — for store discounts. Manufacturer coupons in some states are taxed on the pre-coupon price.
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Last updated: 2026-07-07