CAC payback period is the number of months for a customer's gross profit to repay acquisition cost, calculated as CAC divided by monthly gross profit. It's a primary unit-economics metric for capital efficiency (shorter payback = capital recycles faster) and risk (longer payback = greater exposure to churn before breakeven). Benchmarks vary by business model: under 12 months is excellent for SaaS, 12-18 months is healthy, 18-24 months is acceptable, and over 24 months is typically problematic. It is the unit-economics metric that's most operationally actionable because it directly answers "when does this customer become profitable?"
The calculation:
Basic formula: