The conversion math that decides whether ads make sense for you

Nobody sells you this calculation, because the answer is often no. An agency quoting ad management has a strong reason to talk about impressions and clicks and a weak reason to talk about what a customer costs you at the end of the chain.

You can run it yourself in ten minutes on the back of a receipt. It is the same arithmetic as a menu item. Cost of goods, labor against it, what is left. If what is left is negative, you do not run the special harder. You change the recipe or you pull it.

What numbers do I need before I look at ads?

Four, and you probably already know three.

Your average job value, meaning what a typical customer actually pays you, not your best month. Your gross margin on that job, meaning what is left after the labor and materials that job consumed. Your close rate, meaning how many inquiries turn into paying customers. And your site conversion rate, meaning what share of visitors inquire at all.

The fourth is the one people skip. It is also the only one in the chain you control directly, and the only one that improves for free once you fix it.

If you do not have a conversion rate yet, get it before you go further. Divide last month's real inquiries by last month's sessions, and that percentage is the number the rest of this depends on.

Take all four from your own records. This matters more than it sounds. The industry is full of published customer-value figures with no source underneath them. The most quoted one in local marketing, that the average new dental patient is worth $850, does not come from the American Dental Association's Health Policy Institute, which is the correct primary source and publishes no such figure. Every circulating version traces back to another marketing page. If you build a spend decision on a number like that, you have built it on nothing. Your own invoices are the only defensible input.

How do I actually run the calculation?

Why does the conversion rate matter more than the click price?

Because it is the multiplier, and everyone negotiates the wrong number.

Owners spend weeks trying to lower cost per click by a few cents. Moving your site conversion rate from three inquiries per hundred visitors to six halves your customer acquisition cost outright, and it does that on organic traffic and referral traffic at the same time. Nobody has to approve a budget increase.

The reason this gets ignored is that click cost is a number on a screen and conversion rate is a set of small unglamorous fixes. Cutting fields off a form is one of them, because every extra field on a contact form costs you submissions and nobody notices the ones that never arrived.

Ads amplify whatever your site already does. If the site converts badly, ads just make you pay to find that out faster.

That is also the case for fixing the page before you turn on spend, rather than after. Paid traffic is unforgiving in a way organic traffic is not. Organic visitors arrive with patience because they went looking for you. Ad clicks arrive cold, mid-scroll, with no loyalty at all.

It is also worth knowing how much demand you already have without paying for it. Patient Prism's dental access report, built on 11,552,668 patient calls across 8,280 locations in 2025, attributes 90% of attributable patient calls to the Google ecosystem, with the Google Business Profile alone accounting for 54% and organic plus paid search another 36%. That is dental, and it is a call tracking vendor's own customer base, so it skews toward more organized practices. The pattern still tells you something: a large share of the phone calls a local business receives arrive through Google surfaces that cost nothing per click.

What if the math does not clear?

You have four levers and they are not equally easy.

Raise job value. Bundle, or stop selling the cheapest thing you offer to people who found you through paid search. This is faster than owners think and it is often the whole answer.

Raise close rate. Answer the phone, respond the same hour, and stop letting inquiries sit overnight. The best evidence here is the 2011 Harvard Business Review study by Oldroyd, McElheran and Elkington, which examined 1.25 million sales leads across 29 business-to-consumer and 13 business-to-business companies and found that firms attempting contact within an hour were nearly seven times as likely to qualify the lead as those trying an hour later, and more than 60 times as likely as those waiting a day. One caveat has to travel with it: a co-author was the founder of the software company whose platform generated the data, so treat it as high quality vendor research published under an editorial masthead. The full picture of what the response time research shows is worth reading before you build a process around it.

Raise conversion rate. Watch what people actually do on the page before you guess. Thirty session recordings will tell you more than a month of theorizing about why visitors leave.

Or reduce wasted clicks. Publishing your prices does this bluntly, and putting a price range on the site is usually a filter rather than a deterrent. People who cannot afford you stop clicking, and you stop paying for them.

If none of the four clears the gap, the honest conclusion is that paid search is not your channel this year. That is a real answer, not a failure.

Where does this calculation break down?

In four places, and you should know all of them before you trust the output.

Attribution. The chain assumes you can tell which customer came from which click. In practice a buyer sees your ad, does not click, searches your name a week later and calls the number on your Google Business Profile. Your ad account records nothing and your organic report takes the credit. The chain is still worth running. Just know it is a floor on ad performance, not a precise reading.

Small numbers. At two or three customers a month, one unusual job moves every ratio in the calculation. Use a quarter of data, not a month, and rerun it each quarter rather than reacting to a bad four weeks.

Seasonality. Cost per click, close rate and job value all move with the season in most local trades. A calculation run in your slow month will talk you out of a channel that works in your busy one.

Agency fees. The chain above prices media only. If someone manages the account, their fee belongs in the acquisition cost. Be careful how you benchmark that fee. The commonly quoted ranges, ten to twenty percent of ad spend, fifteen percent as standard, a few hundred dollars a month for small accounts, come from agency blogs quoting other agency blogs. No survey with a disclosed sample supports any of them. A quoted fee is a fact about that agency, not an industry benchmark, and you should treat anyone presenting it as the latter with appropriate suspicion.

What to do this week

Write your four numbers on one sheet of paper. Job value, gross margin, close rate, conversion rate. If you cannot fill in all four, the missing one is your week's work.

Run the hundred-click calculation once at your current conversion rate, then again at double it. The difference between those two results is your budget for fixing the website, and it is usually larger than the quote you were dreading.

Add the management fee to the acquisition cost line and run it again. If the answer changes sign, that is the decision.

If a redesign is already scheduled, sequence it before the ad spend, and protect what you have while you do it, because a migration handled carelessly costs you the rankings you already earned.

Questions about your ad math?

Email me at eric@seod.com with three numbers: your average job value, your rough close rate, and the cost per click you are being quoted. I will run the full chain and send back the customer acquisition cost, plus the conversion rate you would need for the spend to clear your margin.

I do this myself and it takes a few minutes. If the math says do not run ads, that is what the reply will say, and it will be the most useful email you get that week.

Otherwise there is more on conversion here.