Customer Acquisition Cost (CAC) is the total cost required to acquire a single paying customer. It is a unit economics metric, meaning it describes the profitability of one unit of the business — one customer — rather than the aggregate business. A business with a low enough CAC relative to what each customer is worth can scale indefinitely. A business where CAC exceeds customer value cannot survive at scale regardless of revenue growth.

The Basic Formula

CAC = Total Sales & Marketing Spend ÷ Number of New Customers Acquired

The scope of "total sales and marketing spend" matters. A narrow definition includes only paid advertising. A full-cost definition includes paid advertising, content production, agency fees, salaries of sales and marketing staff, CRM software costs, and any other expense incurred to attract and convert customers. Full-cost CAC is the more accurate figure for strategic decisions.

Example: A company spends $30,000 per month on ads, $8,000 on a marketing manager's portion of salary, $2,000 on tools and software, and acquires 200 new customers. CAC = $40,000 ÷ 200 = $200 per customer.

CAC:LTV Ratio — The Viability Test

Customer Lifetime Value (LTV) is the total net revenue a customer generates over their relationship with the business. The CAC:LTV ratio determines whether the acquisition cost is sustainable:

  • LTV:CAC below 1:1 — The business loses money acquiring each customer. Non-viable without changes.
  • LTV:CAC of 1:1 to 3:1 — Marginally viable but likely unprofitable when overhead is included.
  • LTV:CAC of 3:1 — Widely cited as the minimum healthy ratio for SaaS and subscription businesses.
  • LTV:CAC of 5:1 or higher — Strong unit economics, typically signals capacity to grow faster.

CAC Payback Period

A related metric: CAC Payback Period (months) = CAC ÷ Monthly Gross Profit Per Customer. This tells you how many months of retained revenue are required to recoup the cost of acquiring the customer. A 12-month payback period means you are in a loss position on every new customer for the first year of their tenure. For businesses with high churn, a payback period longer than average customer tenure is a structural problem.

Blended vs Channel-Level CAC

Blended CAC averages acquisition cost across all channels and often masks wide variation. Channel-level CAC separates paid search, social, organic, referral, and direct acquisition into separate figures. A blended CAC of $200 might consist of $80 from organic search (excellent), $220 from paid social (acceptable), and $450 from paid search (above LTV — loss-making channel). Blended reporting obscures the need to cut or fix the $450 channel.

Use the USECALC Conversion Rate Calculator and ROI Calculator together to model your acquisition economics before committing to a channel budget.