The total cost to acquire one new paying customer. All-in, including salaries.
CAC = (total sales + marketing spend) ÷ (new customers acquired). Most teams calculate it too narrowly, just ad spend, and then wonder why their CAC looks great but their business struggles. True CAC includes salaries, software, content, everything you spent on acquisition. The broader you count, the more honest the number.
CAC is half of the unit economics equation. Paired with LTV, it tells you whether your business can grow profitably. Without knowing both, you're flying blind. Every growth decision should start by asking: what's this do to CAC?