Working out a sale price
To take a percentage off, multiply the price by (1 − discount). A $80 item at 25% off costs 80 × 0.75 = $60. Many sales then add an "extra 10% off" at checkout, or you stack a coupon. That second discount applies to the already reduced price, not the original one.
Worked example
An $80 jacket is 25% off, with an extra 10% off at the register:
80 × 0.75 × 0.90 = $54.00
You save $26, which is 32.5% of the original price, not the 35% you might expect from adding 25 and 10. Stacked discounts always add up to less than their sum.
Quick mental math
- 10% off: move the decimal point one place left and subtract.
- 20% off: take 10% twice.
- 25% off: divide by 4 and subtract.
- "Buy one, get one 50% off" on two equal items is 25% off each.
Sales tax, where it applies, is added to the discounted price.
How this works
The page multiplies the price by one minus the first discount, then by one minus the extra discount. The amount saved is the original price minus the final price, and the effective discount is the saving divided by the original price. Tax is not included. Everything runs in your browser.
Frequently asked
How do I calculate a percentage discount?
Multiply the price by (1 − discount). 30% off $59.99 is 59.99 × 0.7 = $41.99.
Are two discounts added together?
No. 25% then 10% is 32.5% off, because the second applies to the reduced price.
How much do I save?
The original price minus the sale price; the page shows both the amount and the percentage.
Is tax included?
No. Add sales tax to the final price where it applies.
Sources
Reviewed Oct 17, 2026 · test vectors fixtures/calculators/everyday/discount-calculator/