Contribution Margin (and the contribution cost behind it)

Run the math on a typical DTC order. Average order value $40. Landed COGS $14, payment and platform fees $2.60, shipping $5.40, ad cost per order $11. Contribution margin: $7, or 17.5%. That's a workable business. Now let the ad cost creep to $18, which happens quietly as auctions tighten, and contribution margin goes to negative $4. Every additional order now costs you $4, and "scaling" means losing money faster.

The formula, and the contribution cost behind it

Contribution margin = revenue minus variable costs. Some sellers call the variable-cost side "contribution cost": everything that scales with each order, and nothing that doesn't. Landed COGS, marketplace referral and FBA fees, payment processing, outbound shipping and packaging, returns at their expected rate, and advertising cost per order. Rent, salaries, software subscriptions and your own pay are fixed costs and stay out of it. The line between the two is the whole exercise. Put a fixed cost into contribution cost and every SKU looks worse than it is; leave a variable cost out and you scale a loser.

Divide by revenue to get the contribution margin ratio. The $40 order above runs 17.5%. That ratio says how much of each new sales dollar survives to cover fixed costs, which makes it the number behind break-even: fixed costs of $28,000 a month at a 17.5% ratio means $160,000 of monthly revenue before you earn a dollar of profit. Push the ratio to 25% and break-even drops to $112,000.

Contribution margin vs gross margin

Gross margin is revenue minus COGS only. On the $40 order it's $26, or 65%, which looks wonderful and says nothing about whether the order made money. Marketplace fees, shipping and ads are where ecommerce profit goes to die, and gross margin ignores all three. Contribution margin is gross margin with the platform, the carrier and the ad auction paid. Gross margin tells you if the product works; contribution margin tells you if the order works.

Where to measure it

Per order, per SKU and per channel. Blended contribution margin across the whole business hides the pattern that matters, which is almost always two or three products carrying ten that lose money after ads. Per-channel matters because the same SKU carries a different contribution cost on Amazon (15% referral plus FBA fees) than on Shopify (3% processing plus your own shipping and ad spend). Sellers who only watch blended P&L profit catch this months late, because strong back-catalog SKUs mask the bleeders. Contribution margin at the SKU and channel level catches it the month it starts.

Common questions

Should ad spend count as a variable cost? For a DTC brand buying paid traffic, yes: cut the ads and orders stop, so the cost belongs to the order. Brand-awareness spend that doesn't tie to orders can sit in fixed costs. Pick a rule and keep it.

What's a good contribution margin for ecommerce? After ads, 15% to 30% is healthy for a DTC brand; marketplace-heavy sellers with little ad spend often run higher. Below 10% there's no room for a fee increase or a freight spike.

Can contribution margin be negative? Yes, and that's the signal to act on. A negative number means each extra order loses money, so growth makes things worse. Fix the price, the ad cost or the shipping before spending another dollar on volume.

All of this needs real landed costs and fees mapped per channel, which is exactly the structure our monthly bookkeeping builds, with SKU-level detail available through custom integrations when the catalog is large. See unit economics for the per-order framework this feeds.