This discount calculator gives you the sale price and the amount saved for any percent off or dollar off, handles stacked discounts ("25% off, then an extra 10%"), and works backwards to find the discount percentage or the original price. Switch on the seller view and it also shows what the discount does to your profit per unit and how many more units you need to sell to earn the same money. Change any number and the result updates as you type.
Discount calculator
Sale price, amount saved, stacked discounts, reverse lookups, and the seller view: what the discount does to your margin.
On this page
- How to use the discount calculator
- How it works: the discount formula
- A worked example, buyer and seller
- What a good discount looks like
- FAQ
How to use the discount calculator
Pick the mode that matches what you know. Percent off and Amount off are the everyday cases. Two discounts stacked is for "extra 10% off clearance" offers, where the second discount comes off the already reduced price. Find the discount % takes an original and a sale price and gives the real percentage off, the quickest check on a "was/now" label. Find the original price works back from a sale price and a percentage.
Quantity multiplies everything, and the optional sales tax field adds tax on the discounted price. If you sell things, open the seller view and enter your cost per unit to see profit and margin before and after the discount, and the extra volume you need to break even on the markdown.
How it works: the discount formula
Every mode is a rearrangement of one relationship: sale price = original price × (1 − discount ÷ 100). The amount saved is the original price minus the sale price.
| Mode | Formula the tool applies |
|---|---|
| Percent off | Sale = Original × (1 − P ÷ 100); Saved = Original − Sale |
| Amount off | Sale = Original − A; Equivalent % = A ÷ Original × 100 |
| Two discounts stacked | Sale = Original × (1 − P1 ÷ 100) × (1 − P2 ÷ 100); Effective % = (1 − Sale ÷ Original) × 100 |
| Find the discount % | P = (1 − Sale ÷ Original) × 100 |
| Find the original price | Original = Sale ÷ (1 − P ÷ 100) |
| Sales tax | Tax = Sale × T ÷ 100, added after the discount |
| Seller view | Profit per unit = Price − Cost; Margin = Profit ÷ Price × 100; Extra units to match profit = (Profit before ÷ Profit after − 1) × 100 |
The tax line applies tax to the discounted price, which is how a retailer-funded discount is treated in California's guidance on coupons, discounts and rebates (CDTFA Publication 113); manufacturer coupons are handled differently, and other states have their own rules, so treat the tax line as an estimate.
The stacked case is where most people go wrong. 25% and then 10% is not 35% off: the second 10% comes off a smaller number, so the effective discount is 32.5%. The tool prints both figures.
The seller formula is the one other discount calculators leave out. A discount comes straight off your profit, so a 25% price cut on a product with a 50% margin removes half your profit per unit. The break-even lift is profit before divided by profit after, minus one. The same arithmetic in the opposite direction is in our price increase calculator.
A worked example, buyer and seller
These numbers are an illustration, not a real store. A pair of headphones lists at $80. The store runs 25% off.
- Sale price: 80 × (1 − 0.25) = $60. Saved: 80 − 60 = $20.
- Add an "extra 10% off" code at checkout: 60 × 0.90 = $54. Total saved is $26, which is 32.5% off, not 35%.
- With 8% sales tax on the $54: 54 × 0.08 = $4.32, so you pay $58.32.
Now the seller's side. The headphones cost the store $40 per unit, including payment fees.
- At $80: profit per unit 80 − 40 = $40, margin 40 ÷ 80 = 50%.
- At $60: profit per unit 60 − 40 = $20, margin 20 ÷ 60 = 33.3%.
- Break-even lift: 40 ÷ 20 − 1 = 1.00, so the store needs 100% more units, double the sales, to earn the same profit it made at full price.
- At $54 (after the stacked code): profit 54 − 40 = $14, and the lift is 40 ÷ 14 − 1 = 1.857, so it needs 186% more units, nearly three times the sales.
That last line is why an "extra 10%" on top of a sale is so expensive for the seller. If you run a store, put your own cost in the seller view before you approve a promotion, and read it next to our break even calculator and Shopify profit margin calculator.
What a good discount looks like
For a buyer, a good discount is measured against a real former price. The FTC's Guides Against Deceptive Pricing say a "was" price only supports a saving claim if it is "the actual, bona fide price at which the article was offered to the public on a regular basis" for a reasonably substantial period (16 CFR Part 233). If a product has been "40% off" for six months, the sale price is the price. Run Find the discount % on the price history you can see, not the label.
For a seller, a good discount is one where the extra volume is realistic. If a 20% discount on a 40% margin product needs 100% more units to break even, ask whether the promotion can plausibly double sales. If not, a smaller discount, a bundle, or free shipping above a threshold usually costs less. Keep the former price honest for the same FTC reason, and make sure the product page still does its job, which our product page checklist covers. The markup calculator does the reverse sum, from cost to price.
What to do next. Buyers: check the effective discount and the tax before you decide. Sellers: set a maximum discount per product from the lift figure, and test one promotion at a time so you can see whether the volume turned up.
Store not converting even with the discount? Website Sales Fix is a review of your store's pages, checkout and pricing with the fixes listed in the order that pays, so you are not discounting to cover a problem a better product page would solve.
FAQ
How do you calculate a discount?
Multiply the original price by the discount percentage and divide by 100 to get the amount off, then subtract it from the original price. For 25% off $80, the amount off is 80 × 25 ÷ 100 = $20, and the sale price is $60. The calculator above does this for any price and percentage, and also runs the sum in reverse.
How do you calculate the discount percentage from two prices?
Subtract the sale price from the original price, divide by the original price, and multiply by 100. A drop from $80 to $60 is (80 − 60) ÷ 80 × 100 = 25% off. Use the Find the discount % mode and the tool does it instantly, which is handy for checking whether a "was/now" label is as big as it claims.
Are two discounts of 25% and 10% the same as 35% off?
No. The second discount is taken from the already reduced price, so the effective discount is smaller than the sum. 25% then 10% off $80 is $80 × 0.75 × 0.90 = $54, which is 32.5% off. The stacked mode shows the price after each step and the true effective percentage.
Is sales tax charged before or after a discount?
For a discount the retailer funds, such as a store coupon or a markdown, tax is normally charged on the discounted price. For a manufacturer coupon, the retailer is reimbursed, so the coupon value usually stays taxable. California's tax authority sets this out in its coupons and discounts guidance, and rules vary by state, so check your own state's page if the amount matters.
How much more do I need to sell to make up for a discount?
Divide your profit per unit before the discount by your profit per unit after it, then subtract one. A product that earns $40 at full price and $20 after a 25% discount needs 40 ÷ 20 − 1 = 100% more units, meaning double the sales, to earn the same total profit. The seller view in the calculator shows this figure for your own cost.
How do I find the original price from a sale price?
Divide the sale price by one minus the discount as a decimal. If you paid $60 after 25% off, the original price was 60 ÷ (1 − 0.25) = $80. The Find the original price mode does this for any sale price and percentage, which is useful when a receipt only shows the amount you paid.
Leave a comment: