A small price reduction can require a surprisingly large increase in sales to preserve the same contribution to overheads and profit. Calculate the hurdle before launching the promotion.
A crowded shop and a profitable promotion can look similar from the pavement. Inside the accounts, they may tell different stories.
Every discount changes the money left from a sale. If the costs of providing the product stay the same, a reduction in the selling price comes out of the amount available to cover overheads and profit. More sales can compensate, but the required increase may be larger than the percentage printed on the offer.
That makes this a useful calculation before Black Friday, a holiday sale or an ordinary “ten percent off” campaign. Start with the economics of the offer, then decide how much additional demand is realistically available.
Begin with contribution per sale
For this decision, contribution means the selling price less the variable costs associated with the sale. These can include the product or materials, variable fulfilment labour, packaging, delivery subsidies and transaction charges. Work with amounts on a consistent tax basis.
Contribution is available to meet fixed costs and then profit. It is not the same as final net profit. Costs that change only when the business adds a shift, hires help or increases capacity also need attention; they may not fit neatly into a constant per-unit assumption.
Business Queensland's guide explains the relationship between sales, costs, break-even and profit. It also cautions that a business can generate substantial turnover while still making a loss. [1]
For a promotion, the practical question is how many sales at the lower contribution will replace the total contribution the business would otherwise expect.
A ten percent discount can require fifty percent more sales
The following is a constructed example in US dollars, not data from a real business. Assume variable cost stays at US$70 per unit, capacity is available and there are no extra promotion costs. Ignore taxes and keep common fixed costs unchanged.
At a normal selling price of US$100, each sale contributes US$30. One hundred sales therefore contribute US$3,000 before fixed costs.
A 10% discount reduces the price to US$90, leaving US$20 per sale. To generate the same US$3,000 contribution, the business must sell 150 units: 50% more than the original hundred.
| Discount | Selling price | Contribution per unit | Units required |
|---|---|---|---|
| None | US$100 | US$30 | 100 |
| 10% | US$90 | US$20 | 150 |
| 20% | US$80 | US$10 | 300 |
| 30% | US$70 | US$0 | No finite volume restores the target under these assumptions |
At 20% off, the business needs three times the original volume, an increase of 200%. At 30% off, every unit contributes zero before fixed costs. Additional volume cannot restore a positive contribution if that per-unit relationship remains unchanged.
This is arithmetic, not a forecast that customers will buy the extra units. It identifies the sales hurdle the promotion must clear.
Use your own numbers
For one product with positive contribution, divide the target total contribution by the proposed contribution per sale. Round up to whole units where necessary.
In the simple example, that is US$3,000 divided by US$20, giving 150 units. If the objective includes an additional campaign cost, include it in the numerator. A US$500 campaign would require US$3,500 of contribution to leave the original US$3,000 after paying for the campaign.
At US$20 per sale, that becomes 175 units. The hurdle is now 75% above the original hundred sales, even though the customer sees the same 10% discount.
For several products, a single average can conceal a change in sales mix. A promotion that moves demand towards the lowest-contribution items may produce a different result from one that sells the same proportions as usual. Calculate important product lines separately where practical.
Check what changes when the shop gets busier
The assumption of constant unit cost is convenient. Test it against the actual operation.
Will increased orders require overtime, additional packing, more delivery trips or a higher service tier? Will a marketplace or payment charge rise with transaction value? Is there a realistic allowance for returns, defects and redelivery?
If an extra US$3 of variable expense reduces the discounted contribution from US$20 to US$17, preserving US$3,000 requires at least 177 units. That is before any additional fixed campaign cost. A small overlooked expense can materially change the volume target.
Australia's business.gov.au pricing guidance advises businesses to plan discounts around their costs and objectives. It identifies legitimate purposes such as attracting customers, encouraging repeat business and clearing unwanted stock. [2]
The purpose should be explicit because different objectives require different evidence. Selling old stock, attracting a new customer and protecting this month's profit are not interchangeable achievements.
Ask which sales are genuinely additional
A customer who would have bought at the normal price may simply take the discount. Another may bring next month's purchase forward. Neither necessarily represents a new long-term customer or an extra sale over the period that matters.
That does not make the promotion pointless. It means the evaluation should include the normal-price sales displaced and what happens afterwards.
Compare the promotion period with an appropriate baseline, and record factors that complicate the comparison: seasonality, stock shortages, a local event or a change in advertising. A busy week alone cannot isolate the effect of a discount.
Where feasible, start with a limited product range or a small test. Watch contribution and the quality of fulfilment alongside unit sales. A campaign that generates complaints or strains delivery capacity may create costs that arrive after the till has stopped ringing.
Clearance stock needs a different decision
The worked example is about preserving contribution on repeatable sales with a continuing unit cost. Existing unwanted stock can require a different analysis.
If an item is perishable, obsolete or unlikely to sell later, the purchase cost may already be committed. Compare what can realistically be recovered through each available option, including future handling, storage and disposal costs. Insisting on an old target margin does not by itself create demand.
That is different from ordering fresh stock to sell under the same low-margin promotion repeatedly. Separate a recovery decision about existing inventory from a sustainable pricing policy for replenishment.
This distinction is especially relevant to small traders with limited storage and cash tied up in stock. The useful question is what the next decision will do to resources that remain available, while still recording the original purchase and any loss honestly.
Protect the customer's trust in the offer
A discount has a commercial meaning only if its comparison is credible. State clearly which products qualify, when the offer ends and what limitations apply. Explain delivery charges and other relevant costs rather than leaving the customer to discover them late in the purchase.
For the United States, the Federal Trade Commission's guides on former-price comparisons distinguish genuine previous prices from artificial prices created to advertise a supposed bargain. That is a specific U.S. reference, not a complete account of the rules in every market. [3]
Check the pricing and advertising requirements that apply where the business sells. More broadly, a business trading on reputation has a reason to make an offer understandable even before a legal question arises.
My view is that a modest, clearly explained saving can serve a long-term relationship better than an impressive percentage attached to an unclear reference price.
Consider alternatives to a blanket price cut
A carefully designed bundle may help customers solve a related problem. A limited clearance offer may release space without reducing prices across the whole range. A service improvement may be more valuable to some buyers than a small discount.
Each option still needs costing. A free gift, extra support or free delivery consumes resources. Describe its benefit honestly and count its cost in the promotion rather than treating it as free to the business.
Keep the offer connected to a specific customer need. An extra item nobody wants is not automatically better value, and a complicated package can make comparison harder. The aim is an offer the business can deliver well and the customer can understand.
A decision sheet before launch
- Objective: what would make the campaign worthwhile—extra contribution, stock recovery or evidence of repeat demand?
- Normal baseline: how many units would likely sell without the promotion?
- Real cost: what changes per sale and what new campaign costs appear?
- Required volume: how many discounted sales meet the stated objective?
- Capacity and cash: can the business fund and fulfil that volume?
- Review: when will results, returns and later customer activity be evaluated?
A discount is a choice about margin, demand and the use of limited resources. Calculate what must happen for it to work, test the assumptions and measure the result. The percentage on the sign is only the beginning of the decision.
Read next
- Why Profitable Small Businesses Run Out of Cash
- The Best Business School in Africa May Not Have a Classroom
Sources and research notes
- Business Queensland, Break-even and profit. The campaign calculations here are the author's illustrations using stated variable-cost assumptions.
- Australian Government, business.gov.au, Choose a pricing strategy, including planning discounts.
- U.S. Federal Trade Commission, Guides Against Deceptive Pricing, 16 CFR 233.1: Former price comparisons. Jurisdiction-specific guidance.
All financial figures are constructed examples; actual costs and demand must be checked. About K.T. Shiri · Editorial standards and corrections.
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