Contribution margin (CM2 and CM3)

Gross margin - revenue minus cost of goods - is the number most DTC brands quote and the number that flatters them. It leaves out everything between making the sale and the customer keeping the product: shipping, payment processing, fulfilment, returns. Contribution margin is what’s left after those variable costs come out, and it’s the number that actually decides whether an order made money.

The convention worth knowing, because operators use it as shorthand:

• CM1 - revenue minus cost of goods. Roughly gross margin.
• CM2 - CM1 minus the variable costs of fulfilling the order: shipping, payment fees, pick-and-pack, returns. The real per-order margin.
• CM3 - CM2 minus the cost of acquiring the customer. What the order actually contributed after you paid to win it.

CM3 is where first-order economics become concrete. It’s usually negative on order one - that’s expected - and the business is the sum of CM3 across a customer’s lifetime turning positive over time.

Why this is the constraint, not a footnote

Contribution margin is the ceiling on everything. It sets the acquisition cost you can afford, because CAC has to fit inside the lifetime contribution. It sets how much you can discount before an order costs you money to ship. It’s why two brands with identical revenue and conversion rates can be one healthy and one dying - the difference is the margin structure underneath.

This is also why high-AOV or bundle-led strategies matter beyond the headline order value. A bigger order spreads the broadly fixed shipping and fulfilment cost across more revenue, so CM2 as a percentage improves as AOV rises. Margin isn’t just a finance concern, it’s a lever the growth team moves.

Where the maths goes wrong

• Costing returns as an afterthought. In apparel especially, return rates of 30-40% wreck CM2, because you pay shipping both ways and often can’t resell at full price. A brand that ignores returns in its margin thinks it’s profitable when it isn’t.
• Treating shipping as fixed when it’s offered free. “Free shipping” is a cost the brand absorbs into CM2. A free-shipping threshold set below the point where the order covers that cost loses money on every order under it.
• Optimising conversion without watching margin. A discount-heavy page lifts conversion and quietly converts CM2 into a rounding error. The conversion report looks great and the contribution doesn’t.