The sale price in one step
Multiply by what is left after the discount. Twenty percent off means you keep 80 percent, so multiply by 0.80.
For the round numbers you can skip the calculator. 10% is one tenth (move the decimal one place). 25% is a quarter. 50% is half. 20% is a tenth taken twice.
What you pay at common discounts
| Discount | $50 | $100 | $200 |
|---|---|---|---|
| 10% | $45.00 | $90.00 | $180.00 |
| 15% | $42.50 | $85.00 | $170.00 |
| 20% | $40.00 | $80.00 | $160.00 |
| 25% | $37.50 | $75.00 | $150.00 |
| 30% | $35.00 | $70.00 | $140.00 |
| 50% | $25.00 | $50.00 | $100.00 |
| 75% | $12.50 | $25.00 | $50.00 |
Sales tax is added after the discount in most US states, so the price you pay at the till is a little above the figures here.
Stacked discounts don't add up
A "20% off, then an extra 10%" deal is not 30% off. The second cut works on the price the first one already lowered, so the total is smaller than you'd expect.
On a $100 item, stacking 20% and 10% leaves you paying $72, not the $70 a flat 30% would give — a real 28% off.
To combine discounts, multiply what's left each time: 0.80 × 0.90 = 0.72. Two 50%-off deals leave you at $25 on $100, a 75% cut, never free.
Common questions
How do I work out 20% off in my head?
Take off a tenth, then a tenth again. On $60 that is $6 and $6, so you save $12 and pay $48. The same trick handles 10% (one tenth) and 30% (three tenths).
Do 20% off and 10% off add up to 30% off?
No. The second discount applies to the already-reduced price, so 20% then 10% is a 28% total cut, not 30%. Multiply the fractions instead: 0.80 times 0.90 is 0.72, meaning you pay 72 percent.
What is 25% off of $80?
A quarter off. A quarter of $80 is $20, so the sale price is $60. Multiplying by 0.75 gives the same answer.
