Customer acquisition cost: calculating it to the signed sale

One campaign shows a cost per lead of €40, another €120. The first looks like the winner. Three months later, the second has signed two contracts and the first none. The figure that settles it is not the platform’s, it is the customer acquisition cost, calculated all the way to the signed sale. This article explains what it contains, how to measure it without fooling yourself and what to compare it with; it is part of our online advertising guides.

Three figures people confuse

The platform counts what it sees: clicks, then conversions, often a submitted form. The sale is decided elsewhere and later. In between, each step loses people, and each step has its own cost.

A low cost per lead can hide a high acquisition cost: all it takes is enquiries that are easy to get and hard to sign. That is the trap described in our guide to sending CRM sales back to Google Ads: as long as the only declared conversion is “form submitted”, the campaign looks for forms.

What goes in the numerator

The budget paid to the platform is only part of the spend. An honest calculation adds up:

• ad spend, at the amount the platform actually billed;
• management fees, an agency’s or the time of the person who runs the account in-house;
• tools: CRM, measurement, consent management, in proportion to their use for acquisition;
• creative: copy, visuals, videos, landing pages;
• sales time spent on those enquiries, including the ones that go nowhere.

The last item is the one most often forgotten, and it is what separates a channel that brings projects from a channel that brings the curious. A campaign that produces many unqualified enquiries costs in qualification calls what it seems to save in clicks.

To make it concrete, with example values rather than market averages: over a month, €3,000 of ad spend, €1,500 of management, €200 of tools and 20 hours of qualification valued at €50 make €5,700. If that month brings 60 enquiries, 15 of them qualified and 3 signed contracts, the cost per lead is €95 and the customer acquisition cost €1,900. Both figures are true; only the second tells you whether the advertising pays.

What you count in the denominator

New customers only

An existing customer who comes back was not acquired by the campaign, even if they clicked an ad. Google Ads can tell the difference: its customer lifecycle goals let you bid higher for new customers, or only for them. Mixing old and new customers flatters the figure without saying anything about acquisition.

Signed sales, not promises

A quote sent is not a customer. Count the signed contract or the first paid invoice, and keep the intermediate steps for day-to-day steering.

Attached to the right month

In B2B, the sale comes weeks after the click. Dividing October’s spend by the contracts signed in October mixes two stories. It is better to attach each customer to the month of their first contact (a cohort) and accept that a month can only be judged once its sales cycle has run. The platform has the same time constraint: according to Google’s FAQ on offline conversions, a conversion tied to a click must happen within 90 days of it.

What to compare the result with

A €1,900 acquisition cost is neither expensive nor cheap in itself: it depends on what a customer brings in, in margin and not in revenue. On an online soft-toy store we work with, rebuilding the real margin from the payment provider’s API gave a gross margin of 60.5%, with product cost at 42.2%. The same work measured 3.2% repeat customers: the first order has to pay for its acquisition almost on its own, because few customers come back to spread it.

In B2B, the question is the length of the contract: a customer signed for three years can justify an acquisition cost that a one-off purchase could not carry. Do the calculation with your real margin, relationship length and renewal rate, not with industry averages.

The setup that makes the calculation possible

The calculation is simple; the data is what is missing. For each signed customer, you need to know where they came from.

1. 01Keep the source.

   Each enquiry arrives with its source, campaign and landing page.

2. 02Track the enquiry.

   The CRM moves it to the contract, through named stages.

3. 03Send the stages back.

   Qualified enquiries and sales flow back to the platform.

4. 04Add up the costs.

   Once a month, spend, management, tools and time, divided by each cohort’s customers.

When measurement is missing, acquisition cost is not calculated, it is guessed. Palmora Property, a real-estate listings site we work with, found this out during its tracking audit: the measurement function had never existed, and every measurement was lost. Once the data flows, the figure can be rebuilt every week without copying anything by hand, as described in our article on automated marketing reporting.

What acquisition cost changes in decisions

Once you have the figure, trade-offs become concrete:

• The test budget is set on the number of enquiries needed to judge: see the minimum budget that gives a signal.
• Useless searches are cut every week: negative keywords lower the numerator without touching customers.
• The page receiving the clicks drives the enquiry rate: why the ad is never the only problem.
• The channel is chosen on the cost of a customer, not of a click: compare Google Ads and Meta, or LinkedIn Ads, whose expensive click can bring cheaper customers.
• Automated campaigns learn from what you declare: Performance Max will aim for customers if you send it customers.
• Retargeting reaches people who already know you: read its share of sales separately, as explained in our article on retargeting without third-party cookies.
• Creative goes into the numerator, including what is produced with AI: what works with generated copy and visuals, and why an ad that overpromises costs trust (AI and disinformation).
• New placements, such as ads in AI answers, are judged by the same rule.
• The agency is judged on this figure rather than on clicks: it is one of the points its contract should contain.

To set up this calculation on your campaigns, from the source of each enquiry to the sales in the CRM, our digital marketing offer starts with measurement.

Frequently asked questions

Sources

1. Google Ads Help, about customer lifecycle goals (new tab)support.google.com
2. Google Ads Help, offline conversion imports FAQ (new tab)support.google.com