Google Ads Case Study: 20.85 ROAS for a London Ecommerce Sewing Supplies Brand

The Starting Point

This client came to me with a Google Ads account that was ticking along but nowhere near its potential. The account had the basics in place — Shopping campaigns, some search coverage — but no real structure behind it. Budget was spread too evenly across products that were performing at completely different levels, and there was no systematic way of identifying what was working versus what was quietly draining the account.

The niche itself — ecommerce sewing supplies — is competitive but not overcrowded. Margins are reasonable, average order values are modest, which means CPC efficiency matters enormously. Getting this right wasn’t about finding some clever secret. It was about applying the right framework consistently over time.

The Strategic Approach: Hero, Sidekick, Villain

1. Audit and classify every campaignRather than reorganising campaigns by product category — which is how most accounts are structured — I reorganised by actual performance data. Every campaign was classified as a Hero (strong ROAS, deserves more budget), a Sidekick (solid but needs support), or a Villain (burning spend without returns).
2. Segment Shopping campaigns by performance tierWithin Shopping, I created four distinct segments: over-index performers (ROAS well above target), near-index performers (close to target, worth pushing), under-index performers (below target, requiring bid suppression or exclusion), and no-index products (no conversion history — held back from main spend).
3. Apply tailored bidding strategies per tierEach tier got a different bidding approach. Over-index performers were given aggressive target ROAS bids to scale revenue. Near-index performers were nudged with moderate target CPA bids. Under-index performers had bids pulled back or were isolated so they couldn’t cannibalise budget from the top performers.
4. Layer Performance Max for retargetingRather than replacing Shopping campaigns with Performance Max — a mistake I see constantly — I used PMax alongside Shopping, with audience signals pointed squarely at warm, previously-engaged shoppers rather than cold prospects. Audience signals guide PMax rather than restrict it — Google can still serve outside them if it predicts a conversion — but weighting the campaign this heavily towards retargeting kept the reporting close enough to isolated that we could read retargeting ROAS separately from prospecting numbers. The PMax retargeting campaigns achieved 31.85 ROAS in isolation.
5. Weekly reviews, monthly structural adjustmentsPerformance wasn’t left to the algorithm. Every week I reviewed search term reports, bid performance, and budget pacing. Monthly, I made structural decisions: moving products between tiers, adjusting campaign budgets based on the previous month’s data, and refining audience signals for PMax.

Why Structure Beats Budget Every Time

The most common request I get from ecommerce clients is: “Should we increase the budget?” In most underperforming accounts, the answer is no — at least not yet.

Increasing budget into a poorly structured account just accelerates waste. What this client needed wasn’t more spend; it needed spend concentrated in the right places. By identifying which products over-indexed on ROAS and funnelling budget towards them, we effectively multiplied return without increasing total investment.

The £0.26 average CPC — 60% below category benchmarks — is a direct result of this discipline. When you stop showing ads on irrelevant queries and stop wasting budget on low-converting products, your quality signals improve, your CTR goes up, and Google rewards you with lower CPCs. It compounds.

What Made This Account Different

• Performance-first architecture — campaigns organised by conversion data, not product catalogues
• Segmentation at every level — product, campaign, and audience tiers all treated separately
• PMax used correctly — retargeting only, never as a blanket replacement for Shopping
• Bidding matched to intent — different strategies for different performance tiers, not one-size-fits-all
• Consistent human oversight — weekly reviews meant problems were caught early, wins were scaled quickly
• No vanity metrics — decisions were made on net advertising profit, not just ROAS or click volume

The Results in Context

A 20.85 ROAS puts this account in the top percentile of Google Shopping performance globally. The industry benchmark for ecommerce Google Ads is approximately 2.87 ROAS — this account ran at more than seven times that figure across a sustained two-year period.

The 10.18% conversion rate is similarly striking. The ecommerce benchmark sits around 3.49%. Achieving 10.18% consistently isn’t about luck or a single well-timed promotion — it reflects that the right traffic was being sent to the right product pages, with bids adjusted to prioritise buyers rather than browsers.

Total conversion value of £674,618 with a net advertising profit of £642,268 means the account was generating roughly £30 in revenue for every £1 spent on ads across the engagement period. That’s the kind of efficiency that transforms what a business can invest back into growth.