CPL vs CAC: What's the Difference?

CPL (Cost Per Lead) is simply ad spend divided by the number of leads generated. It's an early, easy-to-game metric - a broader targeting setting or a shorter form can drop CPL while quietly dropping lead quality along with it.

CAC (Customer Acquisition Cost) is the fully-loaded cost of turning a stranger into a paying customer - ad spend, plus sales time, plus any tools or commissions involved, divided by the number of new customers.

A campaign can have an excellent CPL and a terrible CAC if the leads it produces rarely close. The fix isn't to ignore CPL - it's a useful early signal - but to always look one step further down the funnel: cost per qualified lead, then cost per customer, before declaring a campaign a win.