Promotion Break-Even Calculator
How many more units a price promotion has to sell just to earn the profit you made before it — from the price, the unit cost and the discount — with the percentage lift that needs, and the profit change if you know the lift a promotion actually brings.
A discount comes straight off the margin, not the price.
How the promotion break-even calculator works
A discount comes straight off the margin, not the price. At a 30% margin a 10% discount removes a third of the profit on every unit, so sales have to rise by half just to stand still. The break-even lift is the margin before over the margin after, minus one — and it is why promotions that "did really well" on volume so often lost money.
Formula: break-even lift = margin_before / margin_after − 1; units needed = current units × (1 + lift)
Worked examples
| Inputs | Break-even sales lift | Note |
|---|---|---|
| 10% off a 30% margin | 50% | needs a 50% lift |
| A thin margin | 166.67% | a huge lift needed |
| A deep discount | 500% | six times the sales |
FAQFrequently asked questions
Why does a small discount need a big lift?
Because the discount comes out of the margin, which is a fraction of the price. Ten per cent off a 30% margin is a third of the profit per unit, so a third more profit-per-unit must be made up in volume — 50% more units.
What lift do promotions actually get?
Twenty to a hundred per cent for a good one, on the promoted line, for its duration — and some of it is sales pulled forward from next month. Compare your expected lift with the break-even honestly.
Should I include the halo?
If the promotion brings customers who buy other things, yes — add the margin on those sales. If it brings bargain hunters who buy only the deal, no.
What about fixed costs?
They do not change with the promotion, so they cancel out. The comparison is contribution before against contribution during.
Is a deeper discount ever worth it?
To clear stock that would otherwise be written down, to win a first order, or to hit a volume rebate. As a repeat tactic on a normal line, rarely — the break-even lift grows faster than the discount.
Where these figures come from
- APICS / ASCM — inventory management terminology — the turnover, safety stock and reorder point definitions used here
- UK Competition and Markets Authority — the UK consumer protection regulator
Last checked: September 2026. These are standard retail and inventory-management definitions.