How to Calculate a Discount Percentage (3 Simple Formulas)
Find the sale price, the amount you save and the discount percentage with three easy formulas, worked examples and a quick mental-math guide.
Whether you are comparing deals or setting your own prices, three formulas cover almost every discount question. Each one answers a different question.
The three formulas
Amount saved = original price × discount rate
Sale price = original price − amount saved
Discount % = (original price − sale price) ÷ original price × 100
Use the decimal form of the rate. 20% is 0.20 and 15% is 0.15.
Want to try it right away? Discount Calculator is free and needs no signup.
Example 1: find the sale price
A $100 item is 20% off. The amount saved is 100 × 0.20 = $20, so you pay $80.
Example 2: find the discount percentage
A jacket was $45 and now costs $36. The difference is $9. Divide 9 by 45 to get 0.20, so the discount is 20%.
Example 3: a price that is not round
An item costs $249 with 15% off. The amount saved is 249 × 0.15 = $37.35, so the sale price is $211.65.
Discounts on a $60 item
| Discount | You save | You pay |
|---|---|---|
| 10% | $6.00 | $54.00 |
| 20% | $12.00 | $48.00 |
| 25% | $15.00 | $45.00 |
| 30% | $18.00 | $42.00 |
| 50% | $30.00 | $30.00 |
Mental math shortcuts
- 10% off: move the decimal point one place to the left.
- 20% off: find 10% and double it.
- 25% off: take a quarter of the price.
- 50% off: cut the price in half.
Use the calculator
Enter the original price and the discount rate and the calculator shows what you save and the final price at once. The preset buttons for 10%, 20%, 30% and 50% save time on common sales.
Common mistakes
- Using the sale price as the base. A discount is always a percentage of the original price.
- Adding two discounts together. 20% off plus an extra 10% off is 28%, not 30%. See stacked discounts.
- Forgetting sales tax. Tax is normally added after the discount.
FAQ
How do I calculate 20% off?
Multiply the price by 0.80. For $50, that is $40.
What is the formula for a discount percentage?
Subtract the sale price from the original price, divide by the original price and multiply by 100.
Does a discount change the sales tax?
Usually yes, because tax is normally calculated on the lower price. Rules vary by state and by coupon type.
How do I find the original price?
Divide the sale price by 1 minus the discount rate. $72 after 20% off is 72 ÷ 0.80 = $90. The full method is in how to find the original price.