Most clothing brands try to measure SEO the same way they measure a Meta ad campaign: spend in, revenue out, divide. That model fails for organic search for a few structural reasons.
First, the revenue lag. A paid ad can return revenue the same day it runs. SEO builds ranking authority over months — category pages for competitive terms like "women's linen trousers" or "sustainable workwear" can take four to eight months to surface in positions that drive meaningful traffic. Measuring ROI at month two will always look like a failure, even for campaigns that eventually perform well.
Second, attribution model mismatch. Most e-commerce dashboards default to last-click attribution. A customer who discovered your brand via an organic search for "ethical denim brands," visited twice more via direct, and then converted after clicking a retargeting ad — that sale gets credited to paid social. SEO delivered the first touchpoint but gets no credit in the report.
Third, fashion's seasonal complexity. A spring/summer collection that ranks well in March generates revenue over a narrow window. If you're measuring annual ROI, that revenue may look small. But if that organic traffic also drives brand discovery that converts in autumn, the attribution trail goes cold.
Getting ROI measurement right for a clothing store means choosing the right attribution model, measuring at the collection or category level rather than site-wide, and building a payback timeline that reflects how search rankings actually mature — not how a paid campaign would behave.