Customer acquisition cost (CAC)

Every new customer costs something before earning anything: advertising, tools, prospecting time, sales salaries. CAC adds up those costs and spreads them across the customers you won.

It is one of the first metrics investors look at, because it answers a simple question: how much do you need to spend to grow? A company whose every customer costs more than it earns grows while losing money.

CAC is always read next to customer lifetime value (LTV), what a customer brings in over the whole relationship. One without the other says little.

The basic formula: CAC = sales and marketing spend for the period, divided by the number of new customers in the period. If you spent 12,000 euros in a quarter and signed 8 customers, your CAC is 1,500 euros.

The hard part is what goes into the numerator. An honest CAC includes salaries or time spent prospecting, tools (CRM, prospecting software, data), advertising, commissions and contractors. Many small companies forget their own time, which produces a flattering and wrong CAC.

Watch the time lag. One month's spend often produces customers the following month, or later if your sales cycle is long. Calculate over long enough periods, at least a quarter, to smooth that effect.

A CAC is neither good nor bad in absolute terms. 3,000 euros per customer is ruinous for a 50 euro monthly subscription and reasonable for a 30,000 euro annual contract. What counts is the ratio to customer lifetime value.

A rule often quoted in SaaS, popularized notably by investor David Skok, aims for a lifetime value at least three times the CAC, and a CAC paid back within twelve months of margin. These are benchmarks for subscription software, not laws: an agency paid upfront does not face the same constraints.

Calculate CAC per channel as well. A blended CAC of 1,500 euros can hide one channel at 400 and another at 4,000. The per-channel number tells you where the next euro should go.

Forgetting human time. If the founder spends ten hours a week prospecting, that time has a cost even if it never appears on an invoice.

Mixing new customers and renewals. A customer who renews their contract was not acquired this quarter. Counting them artificially lowers CAC.

Crediting each customer to the last channel touched. A prospect who read your posts for six months and then answered a message was acquired by both. Imperfect as it is, logging the main source of each customer prevents absurd conclusions.

The strongest lever often sits at the top: better targeting. Every off-target prospect consumes time, invitations and follow-ups with no chance of signing. A tighter target lowers contact volume and raises the close rate, which lowers CAC.

Second lever: warm sources. People who have already shown interest (a profile visit, a reaction to a post, a referral) cost far less to convert than a stranger, because they reply and book meetings more often.

Third lever: time spent per customer. Automating what repeats, such as research, invitations, follow-ups and first replies, frees billable hours. Keep human time for what really needs it: the call, the proposal, the negotiation.

The math follows the same logic. Add the cost of your tools and the value of the time spent searching, writing, following up and replying, then divide by customers signed through LinkedIn. Human time is often the heaviest line: every conversation takes reading, replying and following up, sometimes for weeks.

To estimate the volume you need, start from your rates. MimikFlow's 2026 LinkedIn Prospecting Observatory (published in French) measured 1.6% observed meetings on invitations sent to strangers, a floor. If you sign one customer per four meetings, that is roughly 250 cold invitations per customer, fewer with warmer sources.

Automating prospecting mostly cuts the time line. MimikFlow finds prospects, sends invitations and messages, follows up and replies up to the meeting, for a monthly subscription listed on the pricing page. Your LinkedIn CAC then becomes, essentially, the subscription plus the time spent on calls, divided by customers signed.