Multiply the price by one minus the discount: 25% off 80 is 60, and you save 20. Add a second discount if the store offers “an extra 20% off sale items”, and a sales tax rate if it is added at the register; the calculator shows the real total discount, which is always less than the two percentages added together.
Stacked discounts multiply, they don’t add
| First discount | Then | Total discount |
|---|---|---|
| 50% | 20% | 60.0% |
| 30% | 10% | 37.0% |
| 25% | 25% | 43.8% |
| 40% | 40% | 64.0% |
| 20% | 15% | 32.0% |
The formula: total = 1 − (1 − first) × (1 − second). Two discounts of 40% leave 60% of 60%, which is 36% of the original price: 64% off, not 80%.
Quick percent-off table
For an item of 100 (multiply for other prices):
| Discount | You pay | You save |
|---|---|---|
| 10% | 90 | 10 |
| 15% | 85 | 15 |
| 20% | 80 | 20 |
| 25% | 75 | 25 |
| 30% | 70 | 30 |
| 40% | 60 | 40 |
| 50% | 50 | 50 |
| 70% | 30 | 70 |
Shortcuts in the store
- 10% off: move the decimal point one place left and subtract. 10% of 45 is 4.50, so you pay 40.50.
- 20% off: take 10% twice. 25% off: take a quarter. 15% off: 10% plus half of that again.
- “Buy one, get one half price”: 25% off the pair. “Three for two”: 33.3% off the three items.
Where tax is added at the register
In the US and Canada, the price on the tag usually excludes sales tax. Take the discount off the tag price first, then add the tax: 60 after the discount plus 8% tax is 64.80. In countries with VAT or GST included in shelf prices, the discount already applies to the price you pay.
Is it really a bargain?
A percentage tells you nothing about the starting price. Before a big sale, prices are sometimes raised so the discount looks larger. Compare the final price with what other stores charge, and with what the item cost a month earlier.
In a store with no signal, the calculator still works once zet4u is saved on your phone (see how).
Frequently asked questions
How do I calculate a discount?
Multiply the price by (1 − discount ÷ 100). 25% off 80 is 80 × 0.75 = 60, so you save 20.
Is 50% off plus an extra 20% off the same as 70% off?
No. The second discount applies to the already reduced price: 100 → 50 → 40, which is 60% off in total.
How do I find the original price from the sale price?
Divide the sale price by (1 − discount). A jacket at 60 after 25% off was 60 ÷ 0.75 = 80.
Is the discount taken before or after sales tax?
Before. Where tax is added at the register, as in the US and Canada, the discount comes off the shelf price and the tax is calculated on what is left.
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