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Platform ROAS ignores cost of goods, shipping and processing fees. Here’s how to build a contribution margin number that actually tells you which campaigns to scale.
The short version
- Platform-reported ROAS is a directional signal, not a profitability number.
- Contribution margin accounts for cost of goods, shipping, discounts and processing fees.
- A channel can post a great ROAS and still lose money on every order.
- Budget decisions should follow margin, with platform ROAS as a secondary diagnostic.
Every ad platform hands you a number that looks like an answer: return on ad spend. It’s easy to read, easy to
compare across campaigns, and easy to build a budgeting habit around. It’s also, on its own, a poor way to decide
where the next rupee of spend should go.
ROAS measures revenue against spend. It says nothing about what it cost to fulfil that revenue. Two campaigns can
report identical 4x ROAS and represent completely different businesses — one profitable, one not — depending on
what sits underneath the top line.
What platform ROAS leaves out #
The platform sees the order value and the ad spend. It doesn’t see the cost of the product, the cost to pack and
ship it, the payment processing fee, or the discount code that shaved 20% off the cart. Every one of those eats
into what’s actually left over — and none of them show up in the dashboard you’re optimising against.
Building a contribution margin number you can actually use #
Contribution margin starts from revenue and subtracts everything that varies with the sale: cost of goods,
shipping, payment processing, and any discount applied. What’s left is what the order actually contributed toward
fixed costs and profit — before ad spend is even in the picture.
- Revenue — the order value, after discounts
- Less cost of goods sold — what the product actually cost you
- Less fulfilment — packaging, shipping, and payment processing fees
- = Contribution margin — what’s left to cover ad spend and overhead
Once that number exists per product or per campaign, ad spend can be judged against it directly: did this
campaign’s contribution margin cover its media cost, with something left over?
ROAS tells you the campaign found buyers. Contribution margin tells you whether finding them was worth it.
Adlux growth team
Running budget decisions on margin, in practice #
This doesn’t mean throwing out platform ROAS — it’s still the fastest signal for spotting a campaign that’s
clearly underperforming. What changes is the order of operations: platform ROAS decides what to look at first,
contribution margin decides what actually gets more budget.
Frequently asked questions #
No — it’s still the quickest way to spot a campaign that’s clearly broken. Just don’t let it be the only number that decides where budget goes.
Product-level is ideal for catalogs where margin varies a lot between SKUs. A blended average by category is a reasonable starting point if that’s more than the data currently supports.
That disagreement is usually the sign the two teams are working from different definitions of cost. Agree on one contribution margin formula, in writing, before the next budget review.
The takeaway #
Platform ROAS is a useful early signal and a poor final judge. The budget that actually grows the business is the
one built on contribution margin — the number that survives contact with cost of goods, shipping and processing
fees.
Written by the Adlux team from live account work. If you want this thinking applied to your catalog, the audit is free and the findings come in writing.