Definition (canonical)
Customer Acquisition Cost (CAC) is the total sales and marketing spend required to win one new customer: `CAC = S&M costs ÷ new customers acquired` in a period. The honesty of the number lives in the numerator: ads AND salaries, tools, agencies, content, events — everything spent to acquire.
Blended vs paid — two questions, two numbers
Blended CAC divides total spend by ALL new customers, organic included — the true average cost of growth. Paid CAC isolates paid channels against customers they brought — the marginal cost of buying one more customer. Both matter, differently: blended feeds unit economics and planning; paid feeds channel decisions. The trap of watching only blended: a strong organic base can mask paid channels acquiring at a loss — until you scale them and the average catches up with you.
Payback period — growth's cash clock
`CAC payback = CAC ÷ (monthly margin per customer)`. CAC of 1,200 with 100 of monthly gross margin = 12 months underwater per customer. This clock decides financing needs: at 12-month payback, every burst of growth consumes a year of cash before returning any — the mechanism behind "we grew ourselves out of money" and half of all burn-rate crises. SaaS convention: under 12 months is good, 12–18 tolerable with strong retention, beyond that growth must be financed deliberately, not by hope.
Managing CAC as a portfolio
CAC is a portfolio of channels, each with its own curve — and every channel's CAC RISES with scale as cheap audiences saturate. Discipline: track CAC per channel monthly; push spend where marginal CAC still clears LTV thresholds; expect and budget the creep; and remember the two structural reducers that outlive any campaign: conversion-rate work (the same spend, more customers) and referrals/word-of-mouth (customers acquiring customers at near-zero CAC).
FAQ
Do salaries really belong in CAC? Yes — a sales team is an acquisition cost. Ads-only "CAC" flatters the number and misleads planning.
Is a high CAC always bad? Only relative to value: enterprise CAC in the tens of thousands is fine against six-figure LTVs. The ratio and payback judge, not the absolute.
How do free trials factor in? Divide by NEW PAYING customers, not signups — trial users are pipeline, not acquisition.
Related: LTV · Unit Economics · Sales Funnel · Burn Rate Reviewed: 2026-07-15 · Sources: unit economics canon