Return on ad spend (ROAS) is the number most e-commerce teams check first. It is useful, but on its own it can lead to the wrong decisions: cutting campaigns that bring new customers, or scaling ones that only capture people who would have bought anyway.
The short answer
No. ROAS tells you revenue per unit of ad spend, as reported by the platform. It does not tell you profit, whether the customer was new, or whether the sale would have happened without the ad. Use it together with margin, new-customer share and a view of total business results.
Why ROAS misleads
It ignores margin. A 4x ROAS on a product with a 20% margin loses money; the same ROAS on a 70% margin product is very healthy. Set a break-even ROAS for each product group first.
It is platform-reported. Google and Meta both claim credit for the same sale depending on attribution windows and modelling. Adding them up usually exceeds your real revenue.
It rewards the bottom of the funnel. Brand search and retargeting often show the highest ROAS because they reach people already about to buy. Cutting prospecting because its ROAS looks low can slowly shrink future demand.
It can be inflated by broken tracking. Duplicate purchase events, refreshed thank-you pages or missing consent handling can make ROAS look better or worse than reality.
What to look at alongside it
- Contribution margin after ad spend: revenue minus product cost, shipping, fees, returns and ads.
- New customer share: how many purchases come from first-time buyers.
- Blended results: total revenue divided by total ad spend across all channels, compared month to month.
- Customer lifetime value: whether customers from a campaign buy again.
- Incrementality tests: pausing a campaign in one region or period to see what really changes.
A simple routine
- Fix tracking first: one purchase, counted once, with consent respected.
- Set break-even and target ROAS per product group based on margin.
- Separate brand, retargeting and prospecting in reporting.
- Review blended results and new-customer share every month.
- Run at least one incrementality test per quarter on your largest channel.
Where we can help
We audit conversion tracking and manage Google Ads and Meta campaigns for e-commerce brands. If your ROAS looks good but profit does not, let’s look at it together.