Discount Calculator
Find the sale price and savings for a percent or amount off, stacked discounts, buy-X-get-Y deals, or the original price behind a sale tag.
The interactive tool loads here when JavaScript runs.
About this toolWhat is the Discount Calculator?
The Discount Calculator answers the questions a sale tag raises: what is 25% off $80, what percent off is "$15 off", what does "an extra 10% off sale prices" really come to, and how much is buy one get one free on five items. Pick the kind of deal and the sale price, savings and total percentage off appear as you type.
Five modes cover the common cases: percent off, amount off, stacked percentages, buy X get Y (free or at a percentage off), and finding the original price from a sale price. Any of them can add sales tax after the discount so you see what you will actually pay at the till.
- Percent off, amount off and stacked discounts
- Buy X get Y at free or at any percentage off
- Reverse mode for the original price
- Optional sales tax after the discount
- Step-by-step working and a shareable link
How to use the Discount Calculator
- Choose the deal: % off, Amount off, Stacked %, Buy X get Y, or Find original price.
- Enter the original price and the discount. For stacked deals add up to three percentages in the order they apply.
- For buy X get Y, enter the price per item, how many items are in the basket, the X and Y of the deal, and how much off the "get" items are (100% means free).
- Optionally enter your sales tax rate to see the final price with tax.
- Read the sale price, the savings and the total percent off, and expand the steps to check the arithmetic.
Worked examples
25% off with 8% sales tax
Input
Price 80, 25% off, tax 8%
Output
Sale price 60.00; you save 20.00; with tax 64.80
Tax is charged on the discounted 60, so it is 4.80 rather than the 6.40 it would be on the full price.
Stacked 20% and 10%
Input
Price 100, 20% then 10%
Output
80.00 after the first, 72.00 after the second; 28% off in total
The second discount takes 10% of 80, not of 100, so the combined saving is 28.
Buy one get one free on five items
Input
Price 12 each, 5 items, buy 1 get 1 at 100% off
Output
Pay 36.00 instead of 60.00; 2 items free; 40% off overall
The odd fifth item is paid in full. Adding a sixth item would be free and bring the deal to exactly 50% off.
Original price behind a sale tag
Input
Sale price 60, 25% off
Output
Original price 80.00
60 / (1 - 0.25) = 80. Adding 25% to 60 would give 75, which is wrong.
Background and insight
A percent-off discount multiplies the price by (1 - discount): 25% off 80 is 80 x 0.75 = 60. Stacked discounts multiply again, so each one applies to a price that is already lower. 20% off then a further 10% off leaves 0.8 x 0.9 = 0.72 of the price, which is 28% off, not 30%. The more and bigger the stacked discounts, the bigger that gap: 50% then 50% is 75% off, not 100%.
Buy-X-get-Y deals depend on how many items you put in the basket. The calculator groups items into sets of X + Y; each complete set earns Y discounted items, and a leftover partial set only earns discounted items after its first X. Five items on buy one get one free is two full pairs plus one item at full price, so you pay for three.
Going backwards from a sale price divides instead of adding: an item that costs 60 after 25% off was 60 / 0.75 = 80, not 60 + 25% = 75. In most US states, sales tax applies to the discounted price for a store discount, which is why tax is added after the discount here.
Common use cases
Comparing two promotions
Check whether "30% off" beats "20% off plus an extra 15%" (it does: the stack is 32% off).
Planning a multi-buy
See how many items to buy so a buy-two-get-one deal works out best.
Checking a receipt
Confirm the till applied the advertised discount and charged tax on the reduced price.
Pricing a sale as a seller
Work out what a markdown or a coupon does to the price before you advertise it.
Tips and limitations
- Percentages taken one after another always add up to less than their sum. Only a single discount of the summed size gives the summed saving.
- Buy-one-get-one deals only reach 50% off with an even number of items; an odd item is paid in full.
- Some stores discount the cheapest item in a mixed buy-X-get-Y basket. This calculator assumes identical prices.
- Manufacturer coupons can be taxed on the pre-coupon price in many states, unlike store discounts.
- An amount off is worth more on a cheaper item: $10 off $40 is 25%, $10 off $200 is 5%.
Frequently asked questions
How do I calculate a percent off a price?
Multiply the price by (100 - percent) / 100. For 30% off $45, multiply 45 by 0.70 to get $31.50. The saving is 45 - 31.50 = $13.50.
Is 20% off and then 10% off the same as 30% off?
No. The second discount applies to the already reduced price, so it is 0.8 x 0.9 = 0.72 of the original, which is 28% off. On a $100 item that is $72, not $70.
How do I find the original price before a discount?
Divide the sale price by (1 - discount). A jacket that costs $68 after 15% off was 68 / 0.85 = $80.
What percent off is buy one get one free?
Exactly 50% when you buy an even number of identical items. With an odd number you pay full price for the last one, so five items work out at 40% off.
Is sales tax calculated before or after a discount?
For a store discount it is usually charged on the discounted price, so you save the tax on the discount too. Manufacturer coupons can be treated differently, depending on the state.
How do I work out what percent off an amount discount is?
Divide the amount off by the original price and multiply by 100. $15 off $60 is 15 / 60 = 25% off.
Is there an in-depth guide to the Discount Calculator?
Yes. “Sales Tax, VAT, Discounts and Tips: Percentages at the Till” covers the background, how it works, common pitfalls and worked examples. Read the full guide.
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