Sale price in one step
Turn the percent into a decimal, subtract it from 1, and multiply. 30% off means ×0.70; 40% off means ×0.60. The amount you save is just the price minus that result. In your head: 10% off is the price with the decimal moved one place; 25% off is a quarter of the price; 50% off is half.
What common discounts leave you paying
| Percent off | $25 | $50 | $100 | $250 |
|---|---|---|---|---|
| 10% | $22.50 | $45.00 | $90.00 | $225.00 |
| 15% | $21.25 | $42.50 | $85.00 | $212.50 |
| 20% | $20.00 | $40.00 | $80.00 | $200.00 |
| 25% | $18.75 | $37.50 | $75.00 | $187.50 |
| 30% | $17.50 | $35.00 | $70.00 | $175.00 |
| 50% | $12.50 | $25.00 | $50.00 | $125.00 |
These are the price you pay, not the amount saved.
Stacked discounts don’t add up
A second discount comes off the already-reduced price, not the original, so stacked percentages are always a bit less than their sum. That is why “extra 10% off” on a 20%-off item is 28% off in total, not 30%.
- Multiply the multipliers. 20% then 10% off is 0.80 × 0.90 = 0.72, an effective 28% off. Add the percents and you overstate the deal.
- BOGO is not a flat 50%. Buy-one-get-one-free is 50% off only when you buy exactly two; at three items it is 33% off.
- $20 off versus 20% off flips at $100. Below $100 the flat $20 wins; above it the percentage wins; at $100 they match.
Common questions
How do I work out a sale price?
Multiply the original price by (1 minus the percent off, as a decimal). For 25% off $80: 80 times 0.75 is $60, saving $20.
Is 20% off plus 10% off the same as 30% off?
No. The discounts multiply, they do not add. 20% then 10% off works out to 28% off, because $100 times 0.80 times 0.90 is $72, not $70.
Does the discount come off before or after tax?
The percent off applies to the price, and in most US states sales tax is then charged on the reduced price. So $80 at 25% off is $60, and tax is added to the $60.
