Retail percentages are designed to be read quickly and calculated slowly. Once you know the one formula underneath, you can check any sale in a few seconds.
The formula
Sale price = original price × (1 − discount ÷ 100). The amount you save is original price × discount ÷ 100.
A $120 jacket at 35% off: 120 × 0.65 = $78.00, so you save $42.00.
Using the calculator
- Open the Discount Calculator.
- Enter the original price and the discount percentage.
- Read the final price and how much you save.
Stacked discounts are not added together
“Take 20% off, then an extra 10% off at the till” is not 30% off. Each discount applies to the price left after the previous one. On $100: 100 × 0.80 = 80, then 80 × 0.90 = 72. The total saving is 28%, not 30%. To do this with the calculator, run the first discount, then enter that result as the new price for the second.
Working backwards from a sale price
If a sale price is $78 after 35% off, the original was 78 ÷ 0.65 = $120. People often make the mistake of adding 35% to $78, which gives about $105 and is wrong, because the 35% was taken from the higher price. Divide by (1 − discount) instead.
Comparing percentage and fixed discounts
“30% off” and “$30 off” are only equal at a price of $100. On a $60 item, 30% off saves $18 while $30 off saves $30. On a $200 item, 30% off saves $60. Compute both before deciding which offer is better for the thing you actually plan to buy.
What the result leaves out
Sales tax, shipping and fees are usually added after the discount, and rules differ by place and retailer. “Up to 70% off” only promises the best discount in the range, not the one on your item. The calculator shows price arithmetic only; it is not financial advice.
Frequently asked questions
How do I find the discount percentage from two prices?
Divide the saving by the original price. For $120 reduced to $78, the saving is $42 and 42 ÷ 120 = 35%.
Is the discount taken before or after tax?
In most places the discount is applied first and tax is added to the lower price, but it varies by country and by retailer, so check the receipt for the total you will really pay.