Customer Acquisition Cost (CAC)
Customer acquisition cost is the average amount a business spends to win one new customer, calculated by dividing total acquisition spend (ads, agencies, tools, and the team time behind them) over a period by the number of new customers gained in that same period.
CAC tells you what it costs to buy a customer, but the number is meaningless on its own. A CAC of 40 is excellent if each customer is worth 200 over their life and ruinous if they spend 30 once and never return. That is why CAC only makes sense read next to customer lifetime value: the ratio between the two, not CAC alone, decides whether growth is profitable.
The honest way to calculate it is to include every cost tied to acquisition, not just the ad invoice. Agency retainers, software, creative, and the salaries of the people running it all belong in the numerator. Leaving them out flatters the figure and hides the real cost of growth.
Trust and conversion are the quiet levers on CAC. The same ad spend buys more customers when the landing experience converts better, and conversion rises when shoppers can verify a claim through reviews and corroborating signals rather than taking it on faith. Lowering friction and raising credibility reduce CAC without touching the budget at the top of the funnel.