How to use
- Pick Price after % off, Find the % off or Stacked discounts.
- Enter the original price, then the discount or the sale price.
- Optional: add your sales tax rate to see what you pay at the till.
Discount formula
Saving = original price × discount ÷ 100
Sale price = original price − saving
Discount % = (original − sale price) ÷ original × 100
Original = sale price ÷ (1 − discount ÷ 100)
For stacked discounts, each one is taken off the price left by the one before.
Examples
- 35% off $140: you save $49 and pay $91.
- $31 down to $13.95: that is 55% off.
- 20% then 10% off $80: $80 → $64 → $57.60. That is 28% off in total, not 30%.
- $56 after 30% off: $56 ÷ 0.7 = $80 originally.
The first two are worked examples from OpenStax Prealgebra.
Why stacked discounts don’t add up
The second discount comes off a price that is already lower, so it saves less than it would on its own. The order doesn’t matter.
| Discounts | Total off | Not |
|---|---|---|
| 20% then 10% | 28% | 30% |
| 30% then 20% | 44% | 50% |
| 25% then 25% | 43.75% | 50% |
| 50% then 20% | 60% | 70% |
| 40% then 10% then 5% | 48.7% | 55% |
| 50% then 50% | 75% | 100% |
To combine discounts yourself, multiply what each one leaves. For 20% then 10%: 0.8 × 0.9 = 0.72, so you pay 72% and save 28%.
How rounding works
Each step is rounded to the cent, as a till would print it. The total percentage is the exact combined rate.
Sales tax, if you add it, is worked out on the price after every discount.
Need a plain percentage instead? Try the percentage calculator. To add tax to any price, use the sales tax calculator.