The total expense required to acquire a new paying customer across marketing, sales, and labor costs.
Customer acquisition cost, or CAC, is acquisition spending divided by the number of new paying customers acquired within a defined measurement scope. It answers a different question from cost per lead: an inquiry has not necessarily become a customer. Returning buyers should not be counted as newly acquired customers merely because they purchased again.
Decide which expenses belong in the calculation. A fully loaded view may include sales time, marketing labor, agency fees, advertising and allocated tools. A narrower channel calculation needs an explicit allocation rule for shared costs. Comparing an SEO figure containing only agency fees with an advertising figure containing all sales costs would be misleading.
Customer acquisition can take longer than the reporting month. A period-based CAC is a useful operating measure, but spending this month may influence customers who buy later. For longer sales cycles, review acquisition cohorts and explain timing assumptions. A channel attribution model also affects which customers are assigned to SEO; CAC alone does not prove that SEO caused every assigned sale.
Takeaway: Compare acquisition costs using the same expense rules and definition of a new customer.
Example
A training company assigns $6,000 of acquisition costs to a quarter and records 20 new paying customers under the same scope. Its period CAC is $300. Counting 40 repeat purchases as new customers would incorrectly lower that figure.
What to check
If no new customers were acquired, report the spending and zero customer count separately; the CAC division is undefined. Avoid a universal “good CAC” without considering margins and payback time.
For more detail, see Customer acquisition cost.