How to calculate a discount
- Type the original price (commas and a currency sign are fine).
- Type the percent off, or tap one of the quick buttons from 10% to 70%.
- Read the sale price and the "You save" line. The breakdown shows each step.
- Optional: add an extra % off for a coupon on top of a sale, and a sales tax % to see what you will actually pay at the till.
The formula is sale price = price × (1 − percent ÷ 100), and the saving is the price minus the sale price. For example,
25% off $80.00 is $80.00 × 0.75 = $60.00, a saving of $20.00.
A quick mental check: 10% of a price is the price with the decimal point moved one place left, so 30% off $59.99
saves about three times $6.00, and the calculator gives $41.99.
Common discounts at a glance
Sale prices for popular discounts on round prices, with the amount saved in brackets.
| Discount | $10.00 | $20.00 | $50.00 | $100.00 |
|---|---|---|---|---|
| 10% off | $9.00 ($1.00) | $18.00 ($2.00) | $45.00 ($5.00) | $90.00 ($10.00) |
| 15% off | $8.50 ($1.50) | $17.00 ($3.00) | $42.50 ($7.50) | $85.00 ($15.00) |
| 20% off | $8.00 ($2.00) | $16.00 ($4.00) | $40.00 ($10.00) | $80.00 ($20.00) |
| 25% off | $7.50 ($2.50) | $15.00 ($5.00) | $37.50 ($12.50) | $75.00 ($25.00) |
| 30% off | $7.00 ($3.00) | $14.00 ($6.00) | $35.00 ($15.00) | $70.00 ($30.00) |
| 40% off | $6.00 ($4.00) | $12.00 ($8.00) | $30.00 ($20.00) | $60.00 ($40.00) |
| 50% off | $5.00 ($5.00) | $10.00 ($10.00) | $25.00 ($25.00) | $50.00 ($50.00) |
| 70% off | $3.00 ($7.00) | $6.00 ($14.00) | $15.00 ($35.00) | $30.00 ($70.00) |
Stacked discounts: why 20% plus 10% is not 30%
When a store offers "an extra 10% off sale prices", the second discount is taken from the already reduced price, not the original. On a $100.00 item, 20% off brings it to $80.00, and 10% off $80.00 is another $8.00, so you pay $72.00. That is 28% off in total, not 30%.
The combined percentage is 100 − (100 − a) × (100 − b) ÷ 100. The order of the two discounts does not matter.
| First discount | Extra discount | Looks like | Real total |
|---|---|---|---|
| 20% | 10% | 30% | 28% |
| 30% | 20% | 50% | 44% |
| 50% | 20% | 70% | 60% |
| 40% | 40% | 80% | 64% |
| 50% | 50% | 100% | 75% |
Two 50% discounts do not make an item free: they leave a quarter of the price. Keep that in mind with "half price plus an extra 50% off" offers.
Adding sales tax
In the US, sales tax is charged on the price after discounts, so the calculator applies it last. With 20% and then 10% off a $100.00 item and 8.25% sales tax, the sale price is $72.00, the tax is $5.94 and the total is $77.94. Manufacturer coupons are an exception in some states, where tax is charged on the pre-coupon price; check your state's rules if the receipt does not match. Prices in the UK and EU usually include VAT already, so leave the tax field empty there.
Finding the original price
If you only know the sale price and the discount, switch to Original price. Divide the sale price by what is left after
the discount: original = sale price ÷ (1 − percent ÷ 100). A $60.00 item marked 25% off was $80.00,
so you saved $20.00. A common mistake is to add 25% back to $60.00, which gives $75.00, not the real $80.00.
Rounding, currencies and limits
- Money is rounded to the cent at each step, the way a till rounds it, so the breakdown always adds up to the total.
- The currency selector only changes the symbol shown ($, €, £ or none). The maths is identical for every currency.
- A discount must be between 0% and 100%, and prices cannot be negative; the calculator tells you when an input is out of range instead of showing a nonsense answer.
FAQ
How do I calculate 20% off a price?
Multiply the price by 0.8, or work out 10% (move the decimal point one place left), double it and subtract. 20% off $50.00 is $50.00 − $10.00 = $40.00.
How do I work out the percentage discount from two prices?
Subtract the sale price from the original price, divide by the original price and multiply by 100. From $80.00 down to $60.00 is 20 ÷ 80 × 100 = 25% off. The percentage calculator's change row does this too.
Is 40% off then 20% off the same as 60% off?
No. Stacked discounts multiply: 0.6 × 0.8 = 0.48 of the price, so the total is 52% off, not 60%.
Is tax calculated before or after a discount?
For store discounts, after: you pay tax on the reduced price. That is how the calculator works when you fill in the sales tax field.
What does "up to 70% off" mean?
Only some items get the full 70%; most are discounted less. Use the calculator with the discount printed on each item's own tag.