What is Customer Acquisition Cost (CAC)?

CAC is the single most useful number for judging whether growth is efficient. It converts every channel, campaign, and headcount decision into one comparable figure: what it actually costs to add a customer. Teams that track revenue growth without tracking CAC frequently discover that they bought their growth at a loss.

The spend side should include everything that exists to acquire customers—paid media, agency and contractor fees, sales salaries and commissions, and the software those teams run on. Excluding sales payroll is the most common way CAC gets understated, and it is why two companies quoting the same CAC are often not measuring the same thing.

CAC on its own is not good or bad. A $500 CAC is excellent for a product with a $6,000 annual contract value and fatal for a $19/month subscription. That is why CAC is almost always read alongside lifetime value and payback period rather than in isolation.

CAC also drifts. It rises as a company exhausts its cheapest audience and pushes into colder segments, and it falls when referral, organic search, and product-led motions start carrying volume. Tracking the trend by channel over several quarters tells you far more than any single quarter's number.