How to work out cost per signed case for Google Ads and for SEO with your own numbers, when each one makes sense, and why most firms should run both at first.
Table of Contents(10 sections)
The short answer
The numbers in this article are examples to show the arithmetic. Replace every one with your own figures from Google Ads, your call tracking and your intake system; that is the only comparison that means anything for your firm.
SEO and PPC side by side
| PPC (Google Ads) | SEO | |
|---|---|---|
| How you pay | Per click | Monthly, for the work |
| When it starts | As soon as the campaign goes live | First measurable movement usually within 60 to 90 days |
| When you stop paying | Visibility stops the same day | Rankings and pages keep working for a time |
| Where it shows | Ad slots, labelled "Sponsored" | Map Pack and organic results, and AI answers that cite pages |
| Control | Exact keywords, budget and hours | Indirect: you influence, Google decides |
| Best for | Leads now, testing which cases are worth it | Lowering cost per case over time, owning visibility |
How to work out PPC cost per signed case
Three numbers from your own account and intake:
- Cost per click — from Google Ads.
- Click-to-lead rate — the share of clicks that call or submit a form.
- Lead-to-signed rate — the share of those leads that become signed cases.
Cost per signed case = cost per click ÷ click-to-lead rate ÷ lead-to-signed rate.
| Example input | Value |
|---|---|
| Cost per click | $50 |
| Click-to-lead rate | 8% |
| Cost per lead ($50 ÷ 0.08) | $625 |
| Lead-to-signed rate | 20% |
| Cost per signed case ($625 ÷ 0.20) | $3,125 |
Notice what the last line depends on. If the same firm signed 10% of leads instead of 20%, the cost per signed case doubles to $6,250 with no change to the ads at all. Intake is part of your advertising cost — see how much a slow intake costs a law firm.
How to work out SEO cost per signed case
Cost per signed case = monthly SEO cost ÷ signed cases from organic search that month.
With an example retainer of $2,000 a month: if organic search signs three cases in a month, that month cost $667 per case; if it signs one, $2,000. In the first two or three months it may sign none while pages are built and indexed, so judge SEO over a longer window — a quarter or a year — not month by month.
Two things make SEO harder to measure than ads: callers who found you on Google Maps often dial the number on your profile directly, and some people see you organically and call later. Call tracking on the profile and asking "how did you hear about us?" at intake close most of that gap.
Local Services Ads: the third option
Google's Local Services Ads appear above the regular ads with a "Google Screened" badge for law firms that pass Google's checks, and they charge per lead rather than per click. They are available for many legal categories in many US areas. For some practices they are the cheapest paid leads; they are worth testing alongside regular search ads and SEO, measured the same way: cost per signed case.
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When PPC makes more sense
- You need cases this month, not this quarter.
- You are entering a new city or practice and want to learn which searches turn into cases.
- Your case values are high enough that a costly click still pays.
- Your website is new and has no organic visibility yet.
When SEO makes more sense
- You plan to serve the same cities and practices for years.
- Your ad costs are rising and you want a channel that does not charge per click.
- Your clients research before calling, which is common in family law, estate planning and immigration.
- You want to appear in the Map Pack and in AI answers, which ads do not buy.
Running both: the sensible order
Keep ads running while organic pages start ranking. As organic search covers particular terms — and you can see it in Search Console and in your call tracking — reduce ad spend on those terms first and move budget to the ones organic does not yet cover. The aim is a lower blended cost per signed case, not switching one channel off on day one.
Both channels count as advertising under bar rules: ABA Model Rule 7.1 on misleading communications applies to ad copy and website copy alike.
Where to find your own numbers
- Cost per click and clicks — Google Ads, by campaign and keyword.
- Calls and forms — call tracking, and form submissions recorded as events in GA4.
- Signed cases by source — your intake or case management system; add a source field if it has none.
- Organic visibility — Google Search Console for impressions and clicks, and your Business Profile's performance report.
Personal injury firms can estimate what visibility gaps and slow intake cost them with the lost case calculator. For timelines, see how long law firm SEO takes, and for the full picture, the complete guide to law firm SEO.
Frequently asked questions
Is SEO cheaper than Google Ads for law firms?
Often over time, not at first. Ads cost per click from day one; SEO costs a monthly fee and takes 60 to 90 days to start moving. Compare the two on cost per signed case with your own numbers rather than on price alone.
How do I calculate cost per signed case from Google Ads?
Divide your cost per click by the share of clicks that become leads, then by the share of leads you sign. For example, $50 per click, 8% of clicks becoming leads and 20% of leads signed gives $3,125 per signed case.
Should I stop Google Ads once SEO starts working?
Not all at once. Reduce spend on the terms organic search already covers, which you can see in Search Console and call tracking, and keep ads on the terms it does not.
Are Local Services Ads better than Google Ads for lawyers?
They charge per lead rather than per click and show a Google Screened badge, so for some practices they are cheaper. Test them alongside search ads and measure both on cost per signed case.
Why does my cost per case change when the ads have not?
Because intake is part of the cost. If the share of leads you sign falls, the cost per signed case rises even when clicks cost the same. Response time is usually the first thing to check.
Mubashar Sharif
LinkedIn ProfileMubashar Sharif is the founder of SearchPrex. Semrush and HubSpot certified, he works on technical SEO, Google Business Profile and local search for US businesses.
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