A promotion can increase revenue and still leave less money to cover the business. Calculate the volume it would need before deciding whether the offer is worth testing.
Start with a comparable baseline
Write down the period you want to review and the orders you reasonably expect without the promotion. Use comparable weekdays, customer mix and product availability. A holiday week and an ordinary week may differ even if you change nothing.
Your baseline is an assumption, not a fact about an alternate future. Record why you chose it. If the business has little history, model a range rather than letting one precise number create false confidence.
Look beyond discounted revenue
Contribution is what remains after the costs included in your model. It still needs to cover general overhead and any costs you have left out. Start with merchandise revenue, then deduct product, fulfillment, net shipping subsidy, payment and other relevant variable costs. Include any extra gift or packing expense caused by the offer.
Do not subtract the discount twice. If you already reduced merchandise revenue, that reduction is already reflected in the calculation. Likewise, keep fixed campaign spending separate from costs you have allocated per order.
Work through an example
Consider a hypothetical regular order with 60 in merchandise revenue, 30 in ordinary variable costs, and a payment fee modeled as 3% plus 0.30. Contribution is 27.90 per order. At 100 orders, the period contributes 2,790 before general overhead.
A 20% discount lowers merchandise revenue to 48. With the same ordinary costs and payment-fee assumptions, contribution becomes 16.26 per order. Add 150 in fixed campaign expense. To preserve the original 2,790, the promotion needs at least 181 orders: 81% more than the baseline.
At only 150 promotional orders, merchandise revenue rises from 6,000 to 7,200. Yet contribution after campaign expense is 2,289, which is 501 below the baseline. All amounts use one currency. These are hypothetical assumptions, not store benchmarks or expected results.
The promotion contribution calculator lets you change these inputs and download the scenario. If per-order contribution is not positive, adding more of those orders does not solve the underlying economics.
Test what the simple model leaves out
A sale can change basket composition, return behavior and the share of new versus existing customers. Free shipping can change net shipping costs. A popular discounted item may sell out while other products remain untouched. Run another scenario with lower revenue per order or higher costs to understand the exposure.
Inspect actual discount combinations in your platform. Shopify supports combinations subject to the discount configuration and applicable restrictions. Test the real cart rather than assuming that an advertised percentage describes the final effective discount on every order.
Ask whether the volume is achievable
A required order count is a planning threshold, not a forecast. What audience can you reach? Is there enough inventory in the variants customers want? Can fulfillment handle the workload? When do supplier and marketing payments leave the account compared with customer payouts?
Also consider whether the offer brings forward purchases that would have happened next week. Campaign-attributed revenue does not establish incremental revenue. Use a suitable comparison where practical, and describe a before-and-after result as directional when other influences remain.
Write a decision before launching
Record the offer, eligible products, dates, cost limit, contribution target and reasons to pause. Name the person who can change or stop the campaign. Afterward, reconcile discounts, returns and actual costs before calling the promotion a success.
If the required volume looks unrealistic, test a smaller discount, a carefully costed bundle or a useful non-price message. The best next step may be improving the product experience rather than increasing promotion intensity.
Platform reference checked October 6, 2026: Shopify discount combinations. Confirm current behavior in your own store.
Want a second pair of eyes?
Use the free worksheet on your own store, or book a 15-minute call to talk through your situation.