How to calculate a discount
A discount calculator takes an original price and a percentage off, and returns how much you save and what you pay. The saving is the price times the discount percentage divided by 100, and the final price is the original minus that saving. For 25% off a price of 80, you save 20 and pay 60.
The formula
- Discount amount = original price × discount % ÷ 100
- Final price = original price − discount amount
You can also get the final price in one step: multiply the original price by (100 − discount %) ÷ 100. A 25% discount means you pay 75% of the price.
The calculator accepts any price of zero or more and a discount between 0 and 100 percent. Both results are rounded to two decimal places.
Worked examples
25% off 80:
- Enter 80 as the original price and 25 as the discount.
- Discount amount = 80 × 25 ÷ 100 = 20.00.
- Final price = 80 − 20 = 60.00.
15% off 49.99:
- Discount amount = 49.99 × 15 ÷ 100 = 7.4985, shown as 7.50.
- Final price = 49.99 − 7.4985 = 42.4915, shown as 42.49.
The calculator rounds only at the end, so the two figures still add up to the original price.
Quick reference: discounts on a price of 50
| Discount | You save | You pay |
|---|---|---|
| 5% | 2.50 | 47.50 |
| 10% | 5.00 | 45.00 |
| 15% | 7.50 | 42.50 |
| 20% | 10.00 | 40.00 |
| 25% | 12.50 | 37.50 |
| 30% | 15.00 | 35.00 |
| 40% | 20.00 | 30.00 |
| 50% | 25.00 | 25.00 |
| 70% | 35.00 | 15.00 |
A handy mental shortcut: 10% of any price is the price with the decimal point moved one place left. Double it for 20%, halve it for 5%.
Stacked discounts
When a shop offers an extra percentage off an item that's already reduced, the second discount applies to the reduced price, not to the original. Run the calculator twice:
- Enter the original price and the first discount. Note the final price.
- Enter that final price as the new original price, with the second discount.
For 20% off 100 followed by an extra 10%: the first step gives 80, and 10% off 80 gives 72.00. That's a combined discount of 28%, not 30%. You can confirm this by entering 100 with a 28% discount, which also returns 72.00.
The general rule is that stacked discounts combine as 1 − (1 − d1) × (1 − d2). For 20% and 10%, that's 1 − 0.8 × 0.9 = 0.28. The order of the two discounts doesn't change the result.
Checking "was" prices
A big percentage off is only meaningful if the original price was real. In the United States, the FTC's Guides Against Deceptive Pricing (16 CFR Part 233) say a former-price comparison should be based on a price at which the item was actually offered in good faith for a reasonable period. Other countries have their own consumer protection rules. When comparing deals, it's often more useful to compare final prices across shops than to compare percentages.
Related calculators
- Percentage calculator: find what percentage one price is of another, or the percent change between two prices.
- GST/VAT calculator: add sales tax to the discounted price.
- Profit margin calculator: check how much margin is left after you discount a product you sell.
- Budget calculator: see how the savings fit into your monthly spending.
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