Discount Profit Calculator
A discount comes straight out of profit. Extra sales needed = (profit per unit before ÷ profit per unit after − 1) × 100. Enter your price, cost and discount to see how much more you have to sell to break even on the promotion.
more units just to earn the same gross profit as at full price.
At other discounts
- 10% off +33.3% units
- 20% off +100.0% units
- 30% off +300.0% units
What the discount costs
- A 20.0% discount removes 50.0% of your profit on every unit.
- For every 100 units you sell today, you'd need to sell 200 on sale to end up with the same gross profit.
- The thinner your margin, the harder this bites — check the figure before you promise a sale, not after.
Discount formula
Formula and worked example
sale price = regular price × (1 − discount ÷ 100) extra sales % = (profit per unit now ÷ profit per unit on sale − 1) × 100 Total gross profit is units × profit per unit. Keeping that total constant while profit per unit falls means units have to rise by the same ratio. Fixed costs don't change the answer, because they're the same either way.
Worked example
- Regular price · cost
- $100 · $60
- Profit per unit now
- $40
- 20% off → sale price
- $80
- Profit per unit on sale
- $20
- Extra sales needed
- 40 ÷ 20 − 1 = 100%
Discount FAQ
Why does a small discount need so many extra sales?
Because a discount comes entirely out of your profit, not out of the price as a whole. On a $100 item that costs $60, a 20% discount takes $20 off a $40 profit — half of it. To earn the same total profit you now have to sell twice as many units.
How do I calculate the sales increase needed after a discount?
Divide your current profit per unit by the profit per unit after the discount, then subtract 1. With $40 profit before and $20 after, that's 40 ÷ 20 − 1 = 1, or a 100% increase in units sold.
What if the discounted price is below my cost?
Then every sale loses money and no amount of extra volume makes up for it — the calculator says so instead of showing a number. Only discount below cost deliberately, for example as a loss leader that sells other products.
What counts as unit cost here?
Every cost that rises with each sale: the product itself, packaging, shipping you pay, payment processing fees, and sales commissions. Leave out fixed costs like rent, which don't change with volume.
Does this account for customers who would have bought anyway?
No — it assumes every sale is made at the discounted price. If some buyers would have paid full price, the real volume increase you need is higher than the figure shown.
Related calculators
Price Increase Calculator
Shows how much sales volume a price increase can lose before profit drops.
Markup vs. Margin Calculator
Converts a cost and price into both markup % and margin %, and shows why they differ.
Contribution Margin Calculator
Calculates contribution margin per unit in dollars and as a ratio of price.