About the Discount Calculator
A discount calculator finds the sale price and the amount saved from an original price and a percentage off. It is the arithmetic behind every sale, and the one most often manipulated in retail presentation.
The formula
Final price = original · (1 − discount / 100)The saving is the original price minus the final price. A 25 percent discount means paying 75 percent of the original.
How to use this calculator
- 1Enter your Original Price ($). The field starts at
120, which you can overwrite. - 2Enter your Discount (%). The field starts at
25, which you can overwrite. - 3Read the result straight away — it recalculates as you type, so there is no button to press. Use Share to copy a link that reopens the page with your exact numbers filled in.
Worked example
| Input | Value |
|---|---|
| Original Price ($) | 120 |
| Discount (%) | 25 |
Result
Final Price: $90.00
You Save: $30.00
Discount Amount: $30.00
Buy 2 for: $180.00
Those are the values the page loads with, so you can reproduce this result yourself and then change one field at a time to see what drives the outcome.
Understanding your result
Stacked discounts do not add. Taking 20 percent off and then a further 10 percent off gives 0.8 × 0.9 = 0.72, a 28 percent total discount rather than 30. The second discount applies to the already-reduced price, which is why the combined figure is always less than the sum.
Working backwards to the original price requires dividing, not adding the percentage back. An item costing 80 after 20 percent off had an original price of 80 ÷ 0.8 = 100, not 96. This is the single most common error in discount arithmetic and it always understates the original.
Things worth knowing
- To reverse a discount, divide by (1 − discount). Adding the percentage back gives the wrong answer.
- Stacked discounts multiply rather than add, so the combined saving is less than the sum of the parts.
- Compare against genuine market price rather than an inflated "was" price, which is often nominal.
- Buy-one-get-one-free is a 50 percent discount only if you wanted two items.
- Percentage off and percentage of are different: 25 percent off means paying 75 percent.
Frequently asked questions
How do I calculate a discount?+
Multiply the price by the discount as a decimal to get the saving, or by (1 − discount) to get the final price directly. A 25 percent discount on 120 gives 120 × 0.75 = 90.
How do I find the original price from a sale price?+
Divide by (1 − discount). An item costing 90 after 25 percent off was originally 90 ÷ 0.75 = 120. Adding 25 percent to 90 gives 112.50, which is wrong.
Do stacked discounts add together?+
No, they multiply. 20 percent off followed by 10 percent off gives a total discount of 28 percent, not 30, because the second applies to the reduced price.
Is a bigger percentage discount always the better deal?+
Not necessarily. Compare final prices, since discounts are applied to different starting points. A 50 percent discount on an inflated price can cost more than 20 percent off a fair one.