ROAS — return on ad spend — is the number every fashion brand watches on Meta. It's on the weekly report. It's in the investor update. It's the metric the media buyer defends or apologises for in every catch-up call.
It's also one of the most misleading numbers in the dashboard.
Why ROAS Lies
Meta's reported ROAS is based on last-click attribution with a view-through window. That means it's taking credit for conversions that happened because of an ad that was served, regardless of whether that ad was the reason the customer bought.
For fashion brands with any organic presence, any email programme, or any influencer activity, this creates a picture of Meta performance that is systematically inflated. The ad gets credited. The other touchpoints disappear.
This leads to budget decisions made on numbers that don't reflect reality. Brands scale channels that look good on ROAS and cut channels that contributed to conversion but didn't receive attribution credit.
What to Look at Instead
The metrics that tell a more honest story are different depending on the brand's stage and business model. New customer acquisition cost. Contribution margin per channel. Blended efficiency across total ad spend relative to total revenue. Customer lifetime value relative to acquisition cost.
None of these are as simple as ROAS. None of them fit as neatly into a weekly report. But all of them produce better decisions.
The fashion brands making the smartest media buying decisions in 2026 have moved past ROAS as a primary metric. They're running with a more complete picture of what their advertising is actually doing.