The cost of winning a customer.

What to include

Count every dollar that exists to win new customers: ad spend on every channel, the agency retainer, affiliate commissions, and the share of your tooling that serves acquisition. Divide by new customers only — a returning customer re-ordering cost you nothing to acquire, and counting them flatters the number. Blended CAC divides that spend by all new customers however they arrived, while paid CAC divides it by the ones your ads brought in — track both, because blended alone can hide a paid channel that is quietly getting expensive. For a channel-by-channel read on ad efficiency, ROAS is the sharper instrument; CAC is the store-wide truth.

What counts as good

A CAC is never good or bad on its own — it only means something next to LTV, what that customer goes on to spend across their whole relationship with you. The old rule of thumb is 3:1: lifetime value at least three times acquisition cost. Below that, growth costs more than it returns; far above it, you are probably underspending on growth. The companion lens is payback period — how many months of gross profit it takes to earn the CAC back. A store that recovers its CAC in three months can reinvest four times a year; one that takes eighteen is lending money to its own marketing. Watch CAC monthly, alongside conversion rate — often the cheapest way to lower it is not cheaper clicks but a site that converts more of the clicks you already pay for.