How discounts are calculated
Stacked discounts don't add up. "20% off, plus an extra 10% off" applies the second discount to the already-reduced price: $100 → $80 → $72. That's a 28% total discount, not 30%. Use the extra discount field to see the real result.
Sales tax is applied after the discounts, which is how most US stores calculate it.
Sale price chart
What you pay after the discount, before tax:
| Price | 10% off | 15% off | 20% off | 25% off | 30% off | 40% off | 50% off |
|---|---|---|---|---|---|---|---|
| $10 | $9.00 | $8.50 | $8.00 | $7.50 | $7.00 | $6.00 | $5.00 |
| $20 | $18.00 | $17.00 | $16.00 | $15.00 | $14.00 | $12.00 | $10.00 |
| $25 | $22.50 | $21.25 | $20.00 | $18.75 | $17.50 | $15.00 | $12.50 |
| $50 | $45.00 | $42.50 | $40.00 | $37.50 | $35.00 | $30.00 | $25.00 |
| $75 | $67.50 | $63.75 | $60.00 | $56.25 | $52.50 | $45.00 | $37.50 |
| $100 | $90.00 | $85.00 | $80.00 | $75.00 | $70.00 | $60.00 | $50.00 |
| $150 | $135.00 | $127.50 | $120.00 | $112.50 | $105.00 | $90.00 | $75.00 |
| $200 | $180.00 | $170.00 | $160.00 | $150.00 | $140.00 | $120.00 | $100.00 |
Shortcut: 10% of a price is the price with the decimal point moved one place left. Double that for 20% off, triple it for 30% off. On $75, 10% is $7.50, so 30% off saves $22.50 and you pay $52.50.
Worked example with tax
A $129.99 jacket is 30% off, with an extra 10% off at checkout and 8% sales tax:
- 30% off: $129.99 × 0.70 = $90.99
- Extra 10% off: $90.99 × 0.90 = $81.89
- Tax: $81.89 × 0.08 = $6.55
- Total: $88.45. You save $48.10, a 37% total discount.
To compare deals quickly, multiply the "pay" percentages: 70% × 90% = 63%, so you pay 63% of the original price.
Frequently asked questions
How do I calculate the original price from a sale price?
Divide the sale price by (1 − discount ÷ 100). For example, $60 after 25% off came from $60 ÷ 0.75 = $80.
Is 40% off the same as 20% off twice?
No. Two 20% discounts give $100 → $80 → $64, a 36% total discount. A single 40% discount gives $60.
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