AM A discount looks simple until you stack two of them, work backward from a sale tag, or check what a promotion does to your margin. This calculator handles all four jobs: sale price and savings, stacked discounts, reverse mode for the original price, and a seller check that compares the discounted price with your unit cost.
Everything runs in your browser. There is no sign-up and no limit on calculations.
How to use the discount calculator
- Enter the original price, for example
80. - Enter the percent off, for example
25. The tool shows the sale price ($60.00) and the amount saved ($20.00). - To stack discounts, add a second percentage. The tool applies it to the already reduced price and shows the combined percent off.
- To work backward, switch to reverse mode, enter the sale price and the percent off, and read the original price.
- If you sell the product, open the seller check and enter your unit cost. You get the profit per unit and margin after the discount, plus the deepest discount you can run before the sale price falls to your cost.
Why stacked discounts do not add up
Two discounts applied one after the other never equal their sum. The second discount is taken from the price that is already reduced, not from the original. A 20% discount followed by a 10% discount leaves you paying 80% of the price, then 90% of that, which is 72% of the original. The total discount is 28%, not 30%.
| First discount | Second discount | Combined discount | Price on a $100 item |
|---|---|---|---|
| 20% | 10% | 28% | $72.00 |
| 30% | 20% | 44% | $56.00 |
| 50% | 10% | 55% | $45.00 |
| 25% | 25% | 43.75% | $56.25 |
The order does not matter. 10% then 20% gives the same 28% as 20% then 10%. What matters is whether your store applies the second discount to the reduced price or to the original. Most "extra 10% off sale items" promotions work on the reduced price, and that is what the calculator assumes.
Reverse mode: find the original price
Reverse mode answers "what did this cost before the sale?" Divide the sale price by what is left after the discount. A $36 item marked 20% off started at $36 / 0.80 = $45. Shoppers use it to check whether a "was" price is honest. Sellers use it to set a compare-at price that produces a specific sale price, such as a $49.99 sale price at 25% off, which needs a regular price of $66.65.
The seller check: margin after the discount
A discount comes straight out of your margin, because your product cost does not change. Enter your unit cost and the calculator shows:
- Profit per unit after discount: sale price minus unit cost.
- Margin after discount: that profit as a percentage of the sale price.
- Break-even discount: the deepest discount that still covers your cost, worked out as 1 minus cost divided by original price.
Example: a product sells for $40 and costs you $22 landed. At 25% off it sells for $30, leaving $8 profit and a 26.7% margin. The break-even discount is 1 minus 22/40, which is 45%. Anything deeper and you lose money on every unit.
Warning: Put every per-order cost into the unit cost if you want a real answer: product, inbound freight, packaging, and the payment and platform fees on each sale. If you only enter the product cost, the break-even discount will look safer than it is. The profit margin calculator helps you build that number first.
How the math works
The calculator uses the same formulas you would use in a spreadsheet:
- Sale price = original price x (1 - discount / 100)
- Savings = original price - sale price
- Stacked price = original price x (1 - d1 / 100) x (1 - d2 / 100)
- Original price = sale price / (1 - discount / 100)
- Margin after discount = (sale price - unit cost) / sale price
Results are rounded to two decimals for display. When you set prices in bulk, rounding can shift the last cent, so check the final price you publish, especially if you use charm pricing like $29.99. If you want to think in markup rather than margin, the markup calculator converts between the two.
Best practices for running a sale
- Set the floor before you set the discount. Know your break-even discount for each product and stay well above it, because returns, ad costs and free shipping thresholds eat the rest.
- Discount by margin, not by habit. A flat 30% off the whole store hurts your low-margin products far more than your high-margin ones. Group products by margin and give each group its own discount.
- Use compare-at prices honestly. Show a real regular price that the product sold at, not an inflated one. Consumer protection rules in many countries treat fake reference prices as misleading.
- Plan the end of the sale. Write down the regular prices before you change anything, so you can restore them exactly.
Putting a store on sale product by product in Shopify or WooCommerce is slow and easy to get wrong. Bulk Edit Pro in AM Jarvis sets sale prices and compare-at prices across many products at once, shows a preview before anything changes, and restores the original prices with one-click revert when the sale ends. The Shopify bulk edit guide covers the built-in options too.
Common mistakes
- Adding stacked percentages. 20% plus 10% is 28% off, not 30%. Promise 30% and your checkout shows 28%, and customers notice.
- Confusing margin and markup. A product with a 50% markup has a 33% margin. A 33% discount on it wipes out the profit completely.
- Forgetting fees scale with price. Percentage-based payment fees drop slightly on a lower sale price, but the fixed per-order fee does not, so cheap items lose margin faster. The Shopify fee calculator shows the exact effect.
- Leaving sale prices live. A forgotten discount can run for weeks after the promotion ends. Set a reminder or use a tool that can revert in one step.