Discount Calculator
Type in a price and the percentage off to see the sale price and what you save - add a second discount to stack them.
How discounts are calculated
A percentage discount takes a slice off the original price. The saving is
price x (discount/100) and the sale price is price - saving. A neat
shortcut is to multiply the price by (1 - discount/100) directly: 25% off means
multiplying by 0.75. So 25% off 80 is 80 x 0.75 = 60, saving 20.
Why stacked discounts are less than they look
"Extra 10% off sale prices" does not add to the sale percentage - it multiplies. Two
discounts of 20% and 10% are applied in sequence: 100 becomes 80, then 80 becomes 72. That is
a 28% effective discount, not 30%. The general rule is that stacking a% and
b% gives an effective discount of a + b - (a x b / 100), always a little
below their sum. The tick box above turns on a second discount and shows the true combined
figure.
Spotting the better deal
Retailers know "30% then extra 20%" sounds bigger than a flat 44%, even though they are identical (0.7 x 0.8 = 0.56, so 44% off). When two offers compete, convert both to an effective percentage and compare. A single 45% beats a stacked 30-plus-20% every time. The same logic applies to a coupon on top of a sale: work the sale price first, then apply the coupon to whatever remains rather than to the original ticket price, or you will overestimate what you save.
Common discount reference
It helps to memorise a few multipliers so you can price a sale in your head. Each percentage off is just the price times the factor below:
| % off | Multiply price by | 50.00 becomes |
|---|---|---|
| 10% | 0.90 | 45.00 |
| 25% | 0.75 | 37.50 |
| 33% | 0.67 | 33.50 |
| 50% | 0.50 | 25.00 |
| 70% | 0.30 | 15.00 |
This is the same core maths as the percentage calculator. If a price includes tax you want to strip first, try the VAT calculator, and for splitting a discounted restaurant bill the tip calculator handles the rest.