Google Ads Case Studies: Which Metrics Actually Prove Agency Performance?
Google Ads case studies are easy to make impressive and surprisingly hard to make useful.
A large percentage increase can sound compelling without telling you whether the starting number was meaningful, how long the comparison lasted or whether anything else changed at the same time.
If you are choosing an agency, read case studies as evidence rather than marketing decoration.
Start with the timeframe
The first question is: when did the result happen?
A useful case study should state the before period and the after period. Without that, you cannot judge seasonality, campaign maturity or whether the comparison is representative.
Digital Womble's Google Ads agency results deliberately use specific dated windows where that is the strongest way to describe the improvement.
Revenue and ROAS are strong only when tracking is strong
Google's negative-keyword guidance reinforces the principle: paid-search optimisation is about excluding irrelevant intent as well as finding demand. Judge changes on query relevance, conversion quality and commercial outcome—not clicks in isolation.
Revenue-linked evidence is usually the most commercially useful. But only if the account can genuinely connect ad spend to sales, bookings or conversion value.
The detailed local-service Google Ads case study documents the spend, attributed new customers and estimated service revenue range, including the caveats behind the calculation.
If revenue attribution is weak, an agency should not manufacture a ROAS story.
CPA and conversion volume
Cost per acquisition or cost per conversion is useful when the conversion itself has commercial value and the tracking event is meaningful.
If conversions rise while cost per conversion falls and spend remains broadly stable, that is usually stronger evidence than a CTR increase on its own.
CPC and CTR
Lower CPC can indicate better efficiency, but cheap clicks are not automatically good clicks.
CTR can show improved relevance or engagement, but a high CTR is not a business outcome.
These metrics become useful when they help explain a wider commercial improvement or when revenue tracking is incomplete and the claim is explicitly limited to traffic efficiency.
Spend reduction
Lower spend can be a positive result if conversion quality is maintained or improved.
For example, cutting irrelevant search terms and improving negative-keyword coverage may reduce wasted media cost while preserving useful traffic.
That is why a good case study should explain what changed rather than presenting a percentage without context.
What to ask an agency about every case study
Use this checklist:
- What exact dates are being compared?
- What was the baseline metric?
- What did the agency change?
- What changed afterwards?
- Is the result revenue-linked, conversion-linked or traffic-only?
- What other changes happened during the same period?
- Is the example typical or deliberately selected?
A credible agency should be comfortable answering those questions.
Proof should lead to a relevant next step
A case study is most useful when it helps you decide whether the same diagnostic framework is relevant to your account.
If the examples around search-term waste, negative keywords, CPC, CPA and conversion efficiency reflect problems you suspect in your own campaigns, the logical next step is a read-only review rather than an immediate retainer.
You can book the £395 Google Ads Account Review or see the wider Google Ads Management service if you already know you want ongoing execution.
Apply the idea without creating more noise
Start with the page's actual job and the reader's next decision. Check the evidence already available, identify the gaps preventing that decision, and improve those before adding another page or campaign. A useful change should make the journey clearer, not simply make the estate larger.
Measure the result against a baseline. For informational content that may mean qualified impressions, clicks and progression to a relevant commercial page; for commercial content it should extend to enquiries, sales or another meaningful conversion. This keeps optimisation tied to business value rather than publishing volume.
A practical review framework
Start with the business outcome rather than the platform metric. Define the conversion that matters, its approximate commercial value and the maximum sensible acquisition cost. Then work backwards through campaign, ad group, search term, ad and landing page. This stops a strong CTR or cheap CPC from disguising poor-quality demand.
Review search terms for intent, not just vocabulary. A query can contain the right keyword and still be informational, navigational or outside the service area. Separate terms that deserve a negative keyword from terms that expose a landing-page or offer problem. Where volume is low, avoid making confident decisions from a handful of clicks; use longer windows and conversion evidence.
Next, check message continuity. The searcher's wording, ad promise and landing-page proposition should describe the same job. If the ad promises a specific service but lands on a generic page, improving bids will not repair the conversion journey. Link paid-search learning back into on-page optimisation so organic and paid traffic are not solving the same intent problem separately.
Finally, document the change and review date. Record spend, qualified conversions, CPA and any downstream revenue signal before and after the intervention. That creates an evidence trail and makes the next optimisation decision easier.