Assumptions
- Amounts are shown to 2 decimals.
- Stacked discounts multiply; no rounding between steps (retailer systems may differ by a cent).
How it is calculated
- Sale price = list × (1 − % ÷ 100). Savings = list − sale.
- Discount rate = (list − sale) ÷ list × 100.
- Stacked: effective rate = 1 − Π(1 − ri ÷ 100). For 30% and 20%: 1 − 0.7 × 0.8 = 0.44.
- Coupon order: "% first" = list × (1 − %) − coupon; "coupon first" = (list − coupon) × (1 − %).
Examples
| Situation | Input | Result |
|---|---|---|
| $50 item, 30% off | 50 · 30% | $35.00 (save $15.00) |
| $89 → $62.30 | two prices | 30% off |
| Outlet 30% + extra 20% at checkout | 100 · [30, 20] | 44% effective, $56.00 |
| 30% off + $5 coupon | 50 · 30% · 5 | % first $30.00 / coupon first $31.50 |
| BOGO | – | = 50% off per item |
Common mistakes
- Inflated "list prices" make the percentage meaningless. FTC guides require a former price to be one at which the item was actually offered in good faith. Compare with recent selling prices.
- Coupons with a cap ("20% off, max $5") equal a flat $5 coupon once the price exceeds $25.
- Shipping and fees are outside the discount math; add them separately.
FAQ
Is 30% off plus an extra 20% the same as 50% off?
No — it is 44% off. $100 → 30% off = $70 → an extra 20% of $70 = $14 → $56. Total saved $44 = 44%. Successive discounts multiply: (1 − 0.30) × (1 − 0.20) = 0.56.
Should the percent discount or the dollar coupon be applied first?
For the shopper, "percent first, then coupon" is better. $50 list, 30% off, $5 coupon: percent first = $30.00; coupon first = $31.50. Most online stores use percent first. Compare both values in the tool.
Does the discount apply before or after sales tax?
In the U.S., discounts reduce the taxable price, so sales tax is charged on the discounted amount in most states. Enter pre-tax prices here and add tax afterwards.
What discount is "buy one get one free"?
Two items for the price of one = 50% off per item. Buy 2 get 1 = 33.3%, buy 3 get 1 = 25% — as long as you would have bought that many anyway.
Is anything saved?
No. Calculations run only in your browser and nothing is transmitted.