Contribution Margin: The One Number That Tells You Which SKUs to Keep

Ask a struggling seller which of their products make money and you'll often get a shrug or a guess. Ask a top seller the same thing and they'll name the number to the cent. The difference isn't talent — it's that the strong operators manage their catalog on one metric most sellers never calculate: contribution margin per SKU. It's the dollars each unit contributes after the costs that move with the sale, and it's the closest thing to a truth serum your product line has. Revenue tells you how busy you are. Contribution margin tells you whether being busy is worth it.

What contribution margin actually is

Contribution margin is your sale price minus all the variable costs of that sale — the referral fee (roughly 15% in most categories), fulfillment, landed cost, and a realistic allowance for returns. What's left is the dollars that unit "contributes" toward your fixed costs and profit. It's deliberately not the same as gross margin, which often ignores fees and returns, and it's a world away from revenue, which ignores cost entirely. A product can have impressive revenue, a respectable-looking gross margin, and a contribution margin near zero once the real fees and returns are subtracted. That last number is the one that decides whether the SKU earns its place.

Build it per SKU, not as a blend

The single biggest mistake is averaging. A blended contribution margin across your whole catalog can look perfectly healthy while hiding products that lose money on every order — the winners quietly subsidize the losers, and you never see it. The fix is to build the number SKU by SKU so each product stands on its own. Lay out, for every product: sale price, referral fee, fulfillment, landed cost, returns allowance, and the contribution that's left. Suddenly the catalog sorts itself into three groups, and what to do with each becomes obvious.

• Scale — high contribution margin and steady sales. These earn their inventory and ad dollars; give them more of both and protect their stock.
• Fix — thin or negative contribution that's caused by a fixable cost: a misclassified fee tier, oversized packaging, or a high return rate. Repair the cost before you judge the product.
• Kill — low contribution that survives every cost fix you try. The capital tied up in it earns more in a SKU that actually contributes; stop reordering and redeploy.

Let the number drive the decisions

Once you have contribution margin per SKU, a lot of hard calls get easy. Which products deserve more ad spend? The high-contribution ones — and your target ACoS should sit comfortably below their contribution, never above it. Where should next quarter's inventory budget go? Toward the SKUs that contribute most per dollar of capital tied up. Which products are quietly dragging the business down? The ones contributing little or nothing despite generating revenue. The metric turns a foggy catalog into a ranked list, and the ranking tells you where to spend your money, your stock, and your attention.

Watch it, because it drifts

Contribution margin is a snapshot, and the inputs move constantly. A fee restructure, a supplier raising your landed cost, a fulfillment surcharge, a price war pulling your sale price down, or a creeping return rate can each turn a contributor into a loser without any single dramatic event. A SKU that looked great last quarter can quietly slip underwater this one. The operators who stay profitable re-run the number whenever an input changes — the kind of ongoing check our profit tools are built to make painless — and keep an eye on their thinnest contributors, so a product that's gone negative gets caught in days rather than after a quarter of silent losses.

Frequently asked questions

How is contribution margin different from gross margin?

Gross margin usually subtracts only the cost of goods, often ignoring marketplace fees and returns. Contribution margin subtracts every variable cost of the sale — referral fee, fulfillment, landed cost, and a returns allowance — so it reflects what the unit truly contributes. It's the more honest number for deciding what to keep.

What contribution margin is high enough?

There's no universal cutoff — it depends on your fixed costs and how fast the product turns. Set your own threshold for the capital and effort each SKU ties up, then judge every product against it. A modest contribution on a fast mover can beat a fat one on a SKU that sits in storage.

Should I kill every low-contribution product?

Not before trying to fix the cost. Thin contribution is often a misclassified fee, oversized packaging, or a high return rate — all repairable. Kill the SKU only if it still can't clear your threshold after you've squeezed those costs; then the capital is better spent on a product that contributes.