Discount Strategy: Measure the Profit You Give Up

Start with contribution per sale

Subtract the variable costs of making and fulfilling an order from its price. Include relevant payment fees, shipping subsidies, commissions, expected returns, and other costs that change with the sale.

Contribution before discount = original price − variable cost

Contribution after discount = original price × (1 − discount rate) − variable cost

This simplified formula assumes variable cost per unit does not change. If the promotion raises fulfillment costs or earns a supplier discount, model those changes separately.

Worked example: 20% off can halve contribution

A product sells for $100 and has a $60 variable cost. Before discounting, each sale contributes $40. A 20% discount reduces price to $80 and contribution to $20.

The business must sell twice as many units just to preserve the original contribution, before paying for the campaign or any extra capacity. Matching revenue would require only 125 units, but that would produce $2,500 of contribution rather than $4,000.

Calculate the required volume lift

When post-discount contribution remains positive:

Required unit multiplier = old contribution ÷ new contribution

Required unit increase = (multiplier − 1) × 100%

If the new contribution is zero or negative, additional units cannot replace the lost positive contribution under this model. Do not report a finite break-even volume in that situation.

The formula assumes every modeled unit receives the discount. For a limited offer, separate full-price and discounted units, and account for customers who switch from a full-price product to the promoted one.

Stacked discounts multiply, not add

Taking 20% off and then another 10% off gives a final price of 100 × 0.80 × 0.90 = $72 on a $100 item. The combined discount is 28%, not 30%.

For two percentage discounts a and b, the combined discount is 1 − (1 − a)(1 − b). Fixed-dollar coupons, caps, minimum spending rules, and shipping charges require their own ordering rules. Show the actual checkout sequence rather than assuming every offer stacks the same way.

Distinguish incremental demand from displaced demand

Some promotion buyers would have purchased at full price. Others may simply buy earlier, stock up, or switch from another product you sell. Those orders do not all represent new demand.

A useful test compares contribution across comparable groups or periods and states the limitations of the comparison. Consider product mix, customer acquisition cost, return rate, repeat purchases, and the timing of later sales. A short revenue spike can be followed by a quieter period because customers bought ahead.

When testing a new-customer offer, avoid counting lifetime value that has not yet been observed as if it were cash in the bank. Separate immediate contribution from an explicit retention forecast.

Consider alternatives to a broad price cut

A narrower offer may preserve more value: a smaller scope, a bundle with a clear cost basis, an off-peak incentive, a quantity threshold, or a benefit that is inexpensive to deliver. Each option still needs a contribution calculation.

Keep advertised conditions clear, including eligibility, exclusions, expiration, and whether shipping or tax is included. Verify applicable consumer-protection requirements with qualified guidance before publishing comparative price claims; this article is not a legal compliance checklist.

Make the result a decision, not a slogan

Set a success measure before the promotion begins. Specify the comparison period, cost scope, expected volume, and maximum contribution you are prepared to sacrifice.

Afterward, reconcile actual discounts, costs, cancellations, and returns. A promotion that misses its profit target can still provide learning, but the learning should not be confused with a profitable campaign.

Use this guide thoughtfully. Examples illustrate a calculation method, not a guaranteed outcome. The usefulness of any result depends on the definitions, measurements, and assumptions used.