A discount changes more than the price a shopper sees. It also changes the contribution each sale produces. Use this calculator before a seasonal promotion, coupon, or clearance event to compare discounted economics with your original price.
How to use this calculator
Enter your original price, variable cost per sale, and selling fees. Choose a percentage or fixed-amount discount. Costs should include product, fulfillment, advertising, and any promotion charges you want to model. Percentage fees are calculated on the resulting selling price.
Formula and assumptions
Contribution = selling price × (1 − percentage fee rate) − variable costs − fixed fees. Sales volume multiplier = original contribution ÷ discounted contribution. Extra units needed = (multiplier − 1) × 100%.
Worked example
A $50 item with $30 variable costs and no extra fees contributes $20. A 20% discount reduces price to $40 and contribution to $10. You would need twice the unit sales—a 100% increase—to preserve the original total contribution.
Common questions
Does a 20% discount mean 20% less profit?
Usually the percentage reduction in contribution is larger because product and fulfillment costs do not fall with the selling price. The impact depends on the original margin and applicable fees.
Will the promotion generate the required sales lift?
This tool calculates the lift required, not the lift customers will produce. Compare the result with your own past promotions and inventory constraints. If contribution becomes zero or negative, extra volume cannot restore positive contribution.
