Definition
The CAC payback period is how long it takes a new customer to generate enough gross profit to cover what it cost to acquire them.
Formula
CAC payback (months) = CAC ÷ (ARPA × gross margin)
where ARPA is average monthly revenue per customer.
Example
CAC is $900, customers pay $100 a month, gross margin is 80%.
Payback = $900 ÷ ($100 × 0.8) = 11.25 months
What's good?
Under 12 months is generally considered strong for small-business SaaS. Longer paybacks can work for enterprise contracts with very low churn, but they need more cash up front.
Why it often matters more than LTV:CAC
Payback doesn't depend on churn, which is the noisiest number an early company has. It also tells you directly how long cash is tied up in each new customer, which matters a lot for bootstrapped companies: money spent on acquisition has to come back before you can spend it again.
How to shorten it
- Raise prices or move customers to annual plans paid up front.
- Lower CAC by cutting the most expensive channels.
- Improve gross margin by reducing the cost to serve each customer.