Discount formulas
- Sale price = original × (1 − discount %)
- Amount saved = original − sale price
- Percent off = (original − sale) ÷ original × 100
- Original price = sale price ÷ (1 − discount %)
- Stacked discounts: final = original × (1 − d₁) × (1 − d₂)
Examples
| Question | Working | Answer |
|---|---|---|
| 30% off $49.99 | 49.99 × 0.70 | $34.99 |
| $120 down to $90 | 30 ÷ 120 | 25% off |
| $45 after 40% off — original? | 45 ÷ 0.60 | $75.00 |
| 20% + extra 10% off $100 | 100 × 0.8 × 0.9 | $72 (28% off) |
| $15 off $60, then 8.25% tax | 45 × 1.0825 | $48.71 |
For store owners: what a discount costs you
A discount comes straight out of your margin, not your revenue. On a product with a 40% margin, a 20% discount halves your profit per unit — you need to sell twice as many to earn the same. Before running a sale, check the new margin with the profit margin calculator.
Quantity-based discounts (“buy 10, save 10%”) usually protect margin better than sitewide sales because they only apply when the order is big enough to make the discount worth it. The tiered pricing calculator helps you set those breaks.
Percent vs fixed-amount discounts
Shoppers read “$10 off” as bigger than “10% off” on items under $100, and “20% off” as bigger on expensive items. For your margin the question is the same either way: what share of the price are you giving away? Switch the discount type in the calculator to compare.