The fundamental formula
Service business Google Ads ROI is conceptually simple: revenue attributable to ads divided by total cost of ads (including agency fees) equals return. In practice, getting to actual numbers requires careful tracking and a clear-eyed view of conversion-to-revenue math.
The metrics that matter
- Cost per click (CPC): What you pay per click. Useful for benchmarking but does not predict ROI directly.
- Click-through rate (CTR): Percentage of impressions that result in clicks. Indicates ad copy quality and audience match.
- Conversion rate: Percentage of clicks that result in a tracked conversion (form submit, phone click, chatbot lead).
- Cost per conversion: CPC divided by conversion rate. This is the cost per lead.
- Lead-to-customer rate: Percentage of leads that become paying customers. This is where most agencies stop measuring.
- Average customer value: Revenue per customer over the lifetime of the relationship.
- Cost per acquisition (CPA): Cost per conversion divided by lead-to-customer rate. This is the cost per actual customer.
- Return on ad spend (ROAS): Revenue divided by ad spend. The ultimate number.
Service business benchmarks
Useful ROAS benchmarks vary by industry but rough ranges:
- Plumbing / HVAC / Electrical (high-value emergency): 5x to 15x ROAS achievable
- Roofing / Construction / Paving (long sales cycle): 3x to 8x
- Auto Glass / Auto Repair (mixed): 4x to 10x
- Legal Services: 3x to 7x
- Pet Services: 4x to 8x
If your ROAS is below 3x for an extended period, something is wrong — either with the campaign structure, the landing page, the conversion tracking, or the qualification of leads.
How to know if your agency is working
Red flags in agency reporting:
- Only impressions and clicks are reported, not conversions or revenue.
- Conversion values are missing or placeholder ($1 per form fill).
- Cost-per-click is reported without cost-per-acquisition.
- Account performance "trends are positive" without specific numbers.
- Negative keywords are not being actively added (you can audit this).
- Search term reports show garbage queries you should not be paying for.
Green flags:
- Weekly review of search terms with active negative-keyword additions.
- Conversion tracking wired with actual dollar values per event.
- Landing page test results discussed.
- Ad copy refresh cadence documented.
- Honest discussion when something is not working.
The right reporting cadence
Weekly one-pager covering: impressions, clicks, CTR, conversions, conversion rate, CPC, cost per conversion, top search terms, top negative keywords added, ad copy changes, landing page changes, recommendations for next week. That is the standard for what your agency should send you weekly.
How we do this
On Grow tier we wire conversion tracking with real dollar values (phone-click $150, form-submit $100, chatbot-lead $80, emergency-CTA $200, customized per client), run weekly account reviews, and send a one-pager every Monday. On Scale tier we do all of that plus a weekly review call. See our Google Ads service for details.
Ready to apply this?
This is the playbook we run on every YelloPost AI build.