Working out a sale price quickly
The sale price is the original price multiplied by what is left after the discount: original × (1 − percent off). For 120 with 40% off that is 120 × 0.6 = 72.
A few multipliers are worth remembering, and you can then do the sum in your head:
- 10% off: multiply by 0.9, or take away a tenth.
- 20% off: multiply by 0.8. 25% off: multiply by 0.75.
- 30% off: multiply by 0.7. 50% off: halve it.
- Three separate 10% reductions are 0.9 × 0.9 × 0.9 = 0.729, so 27.1% off, not 30%.
The calculator also takes the sum the other way: enter the sale price and the percent off under Find the original price to see what an item cost before the sale.
Coupons on top of a sale
An extra percentage off already reduced prices multiplies with the sale. Take 40% off 100 to get 60, then an extra 20% off to get 48. You paid 52% less than the original, not 60%, because the second discount was worked out on 60 and not on 100.
Stacked percentages always give less than their total. The more discounts you stack, the larger the gap. The calculator shows the combined discount so you can compare an offer of "40% plus 20%" with a plain 50% off.
Reading a was and now price
A percent off is only as honest as the price it starts from. A ticket that says was 120, now 90 is 25% off by arithmetic: (120 − 90) ÷ 120. Whether 120 was a price people really paid is another question, so compare with other shops before you treat a big percentage as a bargain.
"Up to 50% off" means that 50% is the largest reduction in the sale, so some items will be reduced by much less. Look at the price of the item you want.
The total at the till
Sales tax, VAT or GST is usually added after the discount. With a tax rate entered, the calculator works it out on the sale price and shows the total: 100 with 25% off is 75, and 8% tax on 75 is 6, so you pay 81. Each amount is rounded to the cent. For the tax on its own, use the VAT calculator.