Discount calculator
- Runs in your browser
- No signup
- Formula shown below
- Reviewed
A discount calculator finds a sale price from an original price and a percentage off, using sale = price × (1 − d ÷ 100). A $120 item with 25% off costs $90 and saves $30. Stacked discounts multiply rather than add, so 25% off followed by a further 10% off gives an effective discount of 32.5%, not 35%.
Result
Sale price
$90.00
sale = price × (1 − d₁ ÷ 100) × (1 − d₂ ÷ 100)
- You save
- $30.00
- Effective discount
- 25.00%
An item priced at $120.00 with 25% off costs $90.00, saving $30.00. That is an effective discount of 25.0%.
How to use the discount calculator
- 01
Enter the original price
Type the list price before any reduction. Use the ticket price, not a previously advertised "was" price if it differs.
- 02
Enter the discount
Type the advertised percentage off, such as 25 for a 25%-off sale.
- 03
Add a second discount if offered
Enter any additional reduction applied at checkout, such as a coupon code stacked on a sale price.
- 04
Add sales tax if you want the till price
Enter your local rate to see what the item actually costs at the register rather than on the shelf.
- 05
Check the effective discount
The rows beneath the result show the total saved and the true combined discount percentage, which is always lower than the sum of the two rates.
The formula
sale = price × (1 − d₁ ÷ 100) × (1 − d₂ ÷ 100); saved = price − sale
- price
- The original list price before any reduction.
- d₁
- The first discount percentage.
- d₂
- Any additional discount applied to the already-reduced price.
- sale
- The price after all discounts.
- saved
- The total reduction in currency terms.
Sequential discounts multiply because the second reduction applies to the already-reduced price, not to the original. Two 50% discounts leave 25% of the original price, not zero.
Worked example
- Original price
- $120
- Discount
- 25%
- Extra discount
- 10%
- Sales tax
- 0%
- Result
- $81.00
The first discount leaves 1 − 0.25 = 0.75 of the price: 120 × 0.75 = $90.00, saving $30. The extra 10% applies to $90, not to $120: 90 × 0.90 = $81.00, saving a further $9. Total saved is $39, so the effective discount is 39 ÷ 120 = 32.5%, not the 35% that adding the two percentages would suggest.
Frequently asked questions
How do you calculate a percentage discount?
Multiply the original price by the discount percentage divided by 100 to find the saving, then subtract it from the price. For 25% off $120, the saving is 120 × 0.25 = $30 and the sale price is $90. Equivalently, multiply the price directly by (1 − 0.25) to reach $90 in one step.
Do stacked discounts add together?
No. Sequential discounts multiply, because each one applies to the price that remains after the previous reduction. Twenty-five percent off followed by 10% off leaves 0.75 × 0.90 = 0.675 of the original, an effective discount of 32.5%. Adding the percentages would overstate the saving by 2.5 percentage points.
What does buy one get one free work out to as a percentage?
Buy one get one free is a 50% discount, provided both items are wanted. Buy one get one half price is a 25% discount across the pair. Buy two get one free is a 33.3% discount across the three. Each figure assumes every included item would have been purchased anyway at full price.
How do you find the original price from a sale price?
Divide the sale price by one minus the discount as a decimal. An item selling for $81 after 32.5% off originally cost 81 ÷ (1 − 0.325) = 81 ÷ 0.675 = $120. This reverse calculation is the practical way to check whether an advertised "was" price is genuine.
Is sales tax charged on the original price or the discounted price?
Sales tax is charged on the discounted price the customer actually pays, in every US state that levies it. A $120 item at 25% off sells for $90, and 8% tax adds $7.20 for a total of $97.20 — not the $9.60 that taxing the $120 list price would produce. Manufacturer coupons are the exception in some states, where tax may apply pre-coupon.
What is a percentage-off versus a fixed-amount coupon worth more?
The basket value decides it. A 20% discount beats a flat $10 off whenever the price exceeds $50, and loses below it. The break-even point is the fixed amount divided by the percentage as a decimal: $10 ÷ 0.20 = $50. Checking that threshold settles which coupon to use when only one may be applied.
Sources
- Guides against deceptive pricing — US Federal Trade Commission
- Sales tax on discounted goods and coupons — Federation of Tax Administrators
- Percentage arithmetic — standards reference — Common Core State Standards Initiative
Last reviewed: · Formula and sources verified by Syed Aqeel Ahmad Gillani. See the methodology for how every calculation is derived.