CAC (Customer acquisition cost)

How to calculate CAC

First, decide which costs count toward CAC (customer acquisition cost). Then divide that total by unique new customers in the same period. Unique means people or companies, not form fills. If the same plumber signs up twice, that is still one customer.

• Paid-only CAC (customer acquisition cost) uses media spend, which is the ads bill.
• Blended CAC (customer acquisition cost) adds salaries, tools, fees, and production, which is the true cost of winning the customer.

Let's take a software company as an example. They sell a monthly tool to plumbing businesses. The software is CRM (customer relationship software) that helps a plumber keep jobs and follow-ups in one place. In Q1 the software company spends $50,000 on Google and LinkedIn ads, $25,000 of salespeople's time following up demos, and $5,000 on tools. That is $80,000. They win 200 new plumbing companies as paying subscribers. $80,000 ÷ 200 = a $400 CAC (customer acquisition cost).

Let's take a software company as an example. They sell a monthly tool to plumbing businesses. Google Ads might show an $80 CPA (cost per acquisition) on those same weeks, because Google is counting demo-request forms, not paying customers, and it is ignoring the sales team. The $80 CPA and the $400 CAC (customer acquisition cost) can both be true. They are different products. Name which CAC you mean, or finance and the ads team will argue about two different things.

Why CAC matters

CAC (customer acquisition cost) is the number you hold against lifetime value (how much a customer is expected to pay you over the whole relationship). Let's take a software company as an example. They sell a monthly tool to plumbing businesses. If it costs the software company $400 to win a plumber who will only ever pay $300, paid growth is a hole. Teams that only watch platform CPA (cost per acquisition: ad spend divided by conversions) often look healthy while full CAC is not.

Agencies get asked for CAC (customer acquisition cost) in pitches even when they only have media CPA (cost per acquisition). Name which one you are showing. A paid-only CAC is still useful. Calling paid-only CAC the company CAC is how a board meeting goes sideways.

How to read CAC

Say which CAC (customer acquisition cost) you mean. Paid-only CAC uses media. Blended CAC uses all acquisition cost. Paid-only is often higher than blended, because organic signups and sales-led customers sit in the same customer count and pull the average down. Report both, or you will scale a channel that does not pay back.

Match the window for CAC (customer acquisition cost) to lifetime value (LTV: what a customer is expected to pay over the whole relationship). A 7-day CAC against a 12-month LTV is a different conversation from a 12-month CAC. Let's take a software company as an example. They sell a monthly tool to plumbing businesses. Payback time (how many months until a plumber's subscription fees cover the software company's $400 CAC) is the cash question hiding inside the ratio. MER (marketing efficiency ratio: all revenue divided by all ad spend) is the closest weekly cousin when you do not have a full CAC build yet. Platform ROAS (return on ad spend) is not CAC either. ROAS is credited revenue, not full cost.

Common CAC mistakes

• Counting demo requests instead of unique new paying customers. Let's take a software company as an example. They sell a monthly tool to plumbing businesses. The software company's form is not a subscriber.
• Leaving salaries, tools, and production out, then calling the leftover number CAC (customer acquisition cost).
• Ignoring payback time. A CAC (customer acquisition cost) that looks fine against a 24-month lifetime value can still break cash if it takes 18 months to earn that money back.