The verdict in three sentences
A promo is only profitable when additional volume offsets the margin given up: at 40 % margin, a 20 % discount requires doubling sales just to break even. The promo type matters as much as the rate: free shipping and bundles protect margin better than a percentage discount. Flash sales are a powerful weapon (+180 % traffic over 48 h) but addictive: too frequent, they destroy the reference price and customers only buy on sale.
Which promo type for which effect?
Not all promos are equal. Percentages attract but cost on every sale; fixed amounts are clear; free shipping is cheap and very effective; bundles raise the basket.
| Promo type | Volume effect | Margin cost | Best use |
|---|---|---|---|
| Percentage (-10 to -30) | Strong | High | Clearance, flash sale |
| Fixed amount (e.g. -5,000) | Medium | Medium | Basket threshold |
| Free shipping | Medium to strong | Low | Lift conversion |
| Bundle (2+1, lot) | Strong | Medium | Raise average basket |
| Free gift | Low | Low | Retention |
The break-even of a discount
The percentage trap: the lower your base margin, the more volume a discount needs to pay off. Here, at 40 % margin, is the additional volume needed to avoid losing money.
| Discount | Margin after discount | Additional volume required | Flash traffic effect (48 h) |
|---|---|---|---|
| -10 % | 33 % | +43 % | +80 % |
| -20 % | 25 % | +100 % | +180 % |
| -30 % | 14 % | +186 % | +250 % |
| Free shipping | ~35 % | +15 % | +60 % |
At -30 %, you must nearly triple sales just to cover costs: reserve that level for pure clearance.
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Mini case study
Aminata runs a fashion store in Lagos, 40 % gross margin, 20,000 FCFA average basket, 300 sales/month. She hesitates between a permanent -20 % and a 48 h -20 % flash sale. Permanently, her margin falls to 25 % and she trains customers to expect discounts. In a 48 h flash, traffic jumps 180 %, she makes 220 sales in two days (vs ~20 expected), i.e. 200 additional sales at 25 % margin = 1M FCFA margin on the event, without degrading her reference price the rest of the month.
FAQ
What discount should I not exceed? Beyond -30 %, most stores at 40 % margin lose money even with strong volume. Reserve deep discounts for end-of-season clearance, never for hero products.
Flash sale or permanent promo? Flash creates urgency and protects your reference price; permanent promos destroy perceived value and train for discounts. Prefer 3-4 framed flash sales a year over continuous discounting.
How do I avoid promo addiction? Limit frequency, vary mechanics (bundle, free shipping over %), and never publish a predictable sale calendar. A customer who can guess the next promo will always wait.
Is free shipping a good promo? Yes: it costs little (5-10 % of the basket) but removes a major psychological barrier. It is often the best impact/margin ratio, especially above a fixed basket threshold.
How do I measure whether a promo paid off? Compare total margin over the promo period to an equivalent normal period, not just revenue. A revenue rise with a total-margin drop means the promo cost you money.
Let's talk about your project. We configure your promo codes, basket thresholds and flash sales with built-in break-even calculation inside your store. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
