BFCM discount math: protect profit before choosing a Shopify offer
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Choose your BFCM discount from the money left after variable costs, not from the percentage a competitor advertises. A promotion can increase orders while leaving too little contribution to pay for acquisition, overhead or the next inventory purchase.
Start with a per-order worksheet, then repeat it for the products you expect the campaign to sell. A storewide average can hide a loss-making bestseller.
Calculate the room available for acquisition
For planning purposes, use:
Contribution before advertising = collected merchandise revenue after discounts − product cost − shipping subsidy − payment fees − packaging − expected variable return/support costs.
Keep taxes collected for remittance separate from merchandise revenue. Use consistent treatment of shipping revenue and costs. This worksheet is a management estimate, not a replacement for your accounting records.
Here is an illustrative example, not an Eggflow customer result:
Item Amount Original merchandise price $100 Revenue after a 20% discount $80 Product cost $40 Merchant-funded shipping $6 Estimated payment fees $3 Packaging $2 Expected variable returns/support allowance $4 Contribution before advertising $25 If the merchant wants to retain $10 per order before fixed overhead, the planning allowance for acquisition is $15, not $25. Recalculate fees and allowances for the actual payment methods and destinations; the fixed estimates above only explain the arithmetic.
Compare three offers on the same basis
Model a percentage discount, a relevant bundle and a gift or shipping incentive. Compare the final contribution and cash required to fulfill each basket.
A bundle is useful when the products belong together and the customer understands the saving. It is less useful when it adds unwanted stock or expensive packaging. A free gift still has a landed cost. A shipping threshold still creates a subsidy that must be funded.
Write down the assumptions rather than hiding them inside a spreadsheet total: product mix, expected discount combinations, fulfillment location, shipping zone and return allowance.
Stress-test the weak baskets
Calculate the outcome for a low-value order, a distant shipping destination, a customer using an eligible second discount, and an order that is later partially returned. These scenarios are a practical way to expose an offer that works only under ideal conditions.
Set an operating rule before launch: for example, pause a specific product campaign when its observed acquisition cost exceeds the amount that product can support. The threshold should come from your own economics, not an industry benchmark.
Check the source data
Shopify's profit reporting depends on recorded product costs. Its gross-profit view is useful, but do not assume it includes every advertising, fulfillment or overhead cost in your business. Reconcile the inputs used for your offer worksheet separately.
Merchant discussion: Which cost is easiest to overlook in your BFCM offer: shipping, returns, payment fees or acquisition?
Continue on Eggflow Blog
For a worked example of the additional contribution from a relevant offer, read Eggflow's Shopify upsell guide.
If shipping is part of your incentive, compare your worksheet with the scenarios in building a profitable free-shipping offer.
Source and further reading
Platform reference checked October 31, 2026. Calculations and scenarios are illustrative editorial examples.
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