There is no industry benchmark that answers this, and any agency that gives you a number before asking what a case is worth to you is guessing. The right budget falls out of four numbers you already have. Here is how to find it.
The short answer
Your Google Ads budget should be the point where the cost of acquiring one more case is still comfortably below what that case is worth to you. Not a percentage of revenue. Not what a competitor spends. Not a number an agency quotes on a first call.
That means the question “what should we spend?” cannot be answered until you can answer “what is a signed case worth, and how many enquiries does it take to sign one?” Most firms cannot answer the second half. That is the actual problem, and it is worth more to fix than any bid adjustment.
Why percentage-of-revenue rules fail law firms
The common advice is to spend some percentage of revenue on marketing. It is popular because it is easy, and it is wrong for two reasons.
First, it is backward-looking. It sets this year’s investment from last year’s results, which means a firm that had a slow year invests less precisely when it most needs pipeline.
Second, and more importantly, it ignores case value entirely. A firm handling matters worth a few thousand and a firm handling matters worth six figures cannot possibly use the same percentage, because the amount they can afford to pay for one signed client differs by orders of magnitude. A rule that treats them the same is not a rule. It is a shrug.
The four numbers you need
Work backward from the case, not forward from the budget.
- Average value of a signed case. Your actual average over the last year, not your best month and not your headline matters. If your case values vary wildly, segment by practice area and run this per area — a firm doing both estate planning and personal injury is running two different businesses.
- Consult-to-signed rate. Of the people who actually get on a call with you, what share retain? This is a number your intake team knows and your marketing team usually does not.
- Enquiry-to-consult rate. Of the people who fill in a form or call, what share reach a real consultation? This is where most firms lose money, and it is almost never an advertising problem.
- What you are willing to pay to sign one case. A share of case value, chosen by you, based on your margin and how much you want to grow. Aggressive firms pay more per case to take share. This is a business decision, not a marketing one.
Putting them together
Multiply your two conversion rates to get your enquiry-to-signed rate. Then:
What you can pay per enquiry = what you will pay to sign one case × your enquiry-to-signed rate
An illustration, using round numbers rather than real ones — substitute your own: if you would pay $2,000 to sign a case, and 25% of enquiries reach a consult, and 40% of consults sign, then 10% of enquiries become cases. You can pay up to $200 per enquiry and break even at your chosen threshold.
Now the budget question becomes tractable. If your market can deliver 50 enquiries a month at or below $200 each, your ceiling is $10,000 a month. If it can only deliver 20 at that price, spending $10,000 means buying 30 enquiries you cannot afford — and your cost per case quietly climbs past the point where the work is worth doing.
This is why “how much should we spend” has no answer in the abstract. The budget is an output.
What actually moves the number
Once you have the model, notice which lever is cheapest to pull.
Halving your cost per click is hard: you are bidding against every other firm in your city, and legal is among the most expensive categories in Google Ads precisely because everyone knows what a case is worth.
Doubling your enquiry-to-consult rate is often much easier, and it does exactly the same thing to your economics. If a quarter of your enquiries reach a consult, the constraint is not your ads. It is what happens in the hours after someone raises their hand — how fast you call back, who answers, and what they say. Firms routinely spend months optimising campaigns while the intake process quietly discards half the demand those campaigns bought.
That is not an advertising insight. It is the reason we look at the whole path from click to signed case before recommending a budget — see how we think about conversion strategy and analytics and attribution.
Before you spend anything
If you cannot currently trace a signed case back to the click that started it, no budget is the right budget, because you will have no way to tell whether it worked. Fix measurement first. It is unglamorous and it is the highest-return thing most firms can do.
Practical minimum: know which enquiries came from paid search, which reached a consult, and which signed. If your CRM cannot tell you that, that is the first project — not a campaign.
Common questions
Is there a minimum viable Google Ads budget for a law firm?
There is a practical floor, but it is set by your market rather than by a universal figure. You need enough monthly clicks to gather meaningful data — if your budget buys only a handful of clicks a month, you will never learn which keywords produce cases, and you will be making decisions on noise. If the numbers in your area do not support enough volume to learn from, paid search may be the wrong first channel, and we will tell you that.
Should a law firm bid on its own brand name?
Usually yes, and it is cheap, but it inflates your reported results. Brand searches are people who already decided to find you, so counting those conversions in your cost-per-case calculation makes your ads look better than they are. Track brand and non-brand separately or you will draw the wrong conclusion about your budget.
How long before I know whether it is working?
Long enough to sign cases, not long enough to see clicks. If your matters take weeks to go from enquiry to retained, then judging the account on a fortnight of click data is judging it on the wrong end. Agree in advance which early indicator you will watch — typically enquiry volume and enquiry-to-consult rate — and which real outcome you will judge on later.
Why is legal so expensive on Google Ads?
Because a signed case is worth a great deal, so every firm in your market can justify a high bid. High cost per click is not a sign the channel is broken; it is a sign the channel works and your competitors know it. The firms that win are usually not the ones bidding most — they are the ones converting more of what they buy.
The honest summary
Your Google Ads budget is not a number someone can hand you. It is what falls out when you know what a case is worth, what share of enquiries become cases, and what you are willing to pay to sign one. Get those, and the budget answers itself. Skip them, and you are picking a number and hoping.
If you want a second set of eyes on those numbers before you commit spend, that is exactly what a strategy call is for. We also work with firms specifically — see marketing for law firms and our approach to Google Ads management.