How many sales a discount needs to pay for itself
In 2026 Black Friday falls on 27 November, the fourth Friday of the month. It is worth planning discounts now: the calculation takes minutes, and a mistake in it eats a month's profit in one weekend.
The basis is simple. Let the price be P, the number of orders Q, the margin m (the share of the price left after all variable costs: purchase, delivery, commission, packaging) and the discount d (also a share of the price).
- Profit from orders before the discount: m × P × Q.
- After the discount each order leaves only (m − d) × P.
- For profit not to fall, the number of orders must become Q′ such that (m − d) × P × Q′ = m × P × Q.
From this Q′ ÷ Q = m ÷ (m − d), and the required growth in orders is:
growth = d ÷ (m − d)
This is not an approximation but an exact equality, provided the price, the margin and the cost per order do not change. If the discount equals or exceeds the margin (d ≥ m), each order brings zero or negative profit, and no growth will pay for it.
Calculated with d ÷ (m − d) at m = 30%. The example is conditional; insert your own margin after all variable costs.
Note the non-linearity. The discount grows from 10% to 25%, that is 2.5 times, while the required growth rises 10 times (from +50% to +500%). The closer the discount to the margin, the sharper the denominator drives it.
A table for your margin
Required order growth for typical combinations. An empty cell means the discount equals or exceeds the margin.
| Margin before discount | Discount 5% | Discount 10% | Discount 15% | Discount 20% |
|---|---|---|---|---|
| 15% | +50% | +200% | — | — |
| 20% | +33% | +100% | +300% | — |
| 30% | +20% | +50% | +100% | +200% |
| 40% | +14% | +33% | +60% | +100% |
| 50% | +11% | +25% | +43% | +67% |
Take the margin not from the price list "purchase – retail" but from the calculation of one order: how to do that is described in the article on unit economics of an online shop. The difference is significant. In the example in that article, a markup of UAH 540 on a UAH 1,200 order leaves UAH 184 after advertising, delivery, commission, refusals and returns, which is 15% of the order. For such a margin a 10% discount needs +200% orders, not +50% as for 30%.
Adjustment for advertising
The formula above silently assumes that the extra orders arrive for free. If paid advertising brings them, each extra order must also pay for its acquisition cost a (in hryvnias).
Profit after the discount on all orders: (m − d) × P × Q × (1 + x). From it we subtract advertising on the extra orders: a × Q × x. Equating to the original profit gives:
growth = d × P ÷ ((m − d) × P − a)
A conditional example: price UAH 1,200, margin 30% (UAH 360), advertising a per extra order.
| Discount | a = UAH 0 | a = UAH 50 | a = UAH 100 |
|---|---|---|---|
| 10% (UAH 120) | +50% | +63% | +86% |
| 15% (UAH 180) | +100% | +138% | +225% |
A 15% discount with UAH 100 of advertising per extra order requires raising orders 3.25 times: +225%. This is why a discount without a strong time limit and without a mailing to the existing base is hard to pay back. How to count the acquisition cost of an order and test a budget is described in the article on the advertising budget of an online shop.
An example with 500 orders
A conditional shop: 500 orders a month, an order value of UAH 1,200, a 30% margin.
- Base profit: 500 × 1,200 × 0.30 = UAH 180,000.
- A 15% discount without the advertising adjustment: +100% is needed, that is 1,000 orders. Profit: 1,000 × 1,200 × 0.15 = UAH 180,000. Warehouse and logistics must withstand a doubling within a few days.
- A 10% discount: +50% is needed, that is 750 orders. Profit: 750 × 1,200 × 0.20 = UAH 180,000.
The data are conditional, but the conclusion carries over to any numbers: the phrase "a 15% discount pays off because sales will grow" without a number for the growth means nothing. A shop that cannot process twice as many orders loses money on a 15% discount at such a margin even if it "works".
There is also an effect the formula does not show: some buyers would have bought on an ordinary day too and are simply getting a discount now. How many depends on the shop and we did not measure it; in the calculation it raises the real required growth.
What to use instead of a discount on the whole range
If the formula shows that the growth is unrealistic, there are three ways not to give away margin on everything:
- A gift instead of a discount. The gift costs you its purchase price while the buyer sees the retail price. A 10% discount on a UAH 1,200 order costs UAH 120, while a gift bought for UAH 60 and retailing at UAH 150 costs half as much.
- A bundle at a fixed price. The discount applies only to a pair of items that already have a high margin, not to the basket.
- A discount on the second item or a free-delivery threshold. It raises the average order value, so the formula works the other way: you add margin rather than give it away.
Count cash on delivery separately: its refusals rise during a sale, and each refusal is delivery there and back. The formula does not include this, so the calculation from the article on cash on delivery is worth repeating with your own refusal rate.
Check before launch
Before announcing a discount, check four things.
- Do you know the margin of one order after delivery, commission and returns?The "purchase – retail" margin overstates the result. No → calculate it, then come back
- Is the discount smaller than this margin?Otherwise every order loses money. No → reduce the discount or limit the range
- Can the warehouse and delivery handle the growth from the formula d ÷ (m − d)?Doubling orders over a weekend needs people and stock. No → a gift, a bundle or a discount on the second item
- Will the extra orders come from your own base rather than paid advertising?For paid ones recalculate with the advertising adjustment. No → build the acquisition cost into the calculation
After the sale compare the result not with revenue but with profit: orders × (m − d) × order value minus advertising. Only this number shows whether the discount paid off.
Our position
A discount on the whole range on Black Friday is worth running only if its growth by the formula d ÷ (m − d) is realistic for the warehouse, delivery and the customer base. At a thin margin without a strong warm-up of the base, a gift, a bundle and a discount on the second item work better.
The position does not apply if the aim is not profit from the sale but winning buyers who will return: then the discount is an acquisition cost and is compared with the cost of acquiring a customer through other channels, not with the weekend's profit. It also does not apply to remnants that would otherwise have to be written off: there you take the purchase price of the remnant instead of the margin.
The formulas were derived and recalculated in code on 17 October 2026; all sums and percentages in the article are calculated. The examples with numbers are conditional and are not data of a specific shop. The date of Black Friday 2026 was determined from the calendar as the fourth Friday of November.