Find the price after a discount and how much you save. Stack an extra discount, add sales tax, or work backwards from a sale price to the original.
How to calculate a discount
Sale price = Original price × (1 − discount ÷ 100)
25% off $80: 80 × 0.75 = $60, so you save $20.
Stacked discounts don't add up
"20% off, then an extra 10% off" is not 30% off. The second discount comes off the already-reduced price: 0.8 × 0.9 = 0.72, which is 28% off. On $100 that's $72, not $70.
Finding the original price
To undo a discount, divide by what's left rather than adding the percent back. If you paid $60 after 25% off, the original was 60 ÷ 0.75 = $80 (adding 25% to $60 would give $75, which is wrong).
How we checked this
Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:
- 25% off $80 = $60 ✓
- 20% then 10% off $80 = $57.60 (28% off, not 30%) ✓
- $60 after 25% off was $80 ✓
Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.
Questions people ask
How do I calculate 30% off?
Multiply the price by 0.7. $50 with 30% off is $35.
Is 20% off plus 10% off the same as 30% off?
No. It's 28% off, because the 10% is taken from the already-discounted price.
How do I find the original price before a discount?
Divide the sale price by (1 − the discount as a decimal). $45 after 40% off: 45 ÷ 0.6 = $75.
Is sales tax added before or after the discount?
In most US states, sales tax is charged on the discounted price.