GlossaryGrowth & analytics
What is the CAC payback period?
Also called: payback period, months to recover CAC
Definition
CAC payback period is the number of months it takes for a new customer's gross profit to repay the cost of acquiring them. Shorter payback means cash comes back sooner to fund more growth.
CAC payback period, explained
The formula: CAC divided by (monthly revenue per customer × gross margin). If it costs $300 to acquire a customer who pays $50 a month at 80% gross margin, each month returns $40 of gross profit, so payback is 300 ÷ 40 = 7.5 months.
Payback matters because it's about cash, not just profitability. LTV can say a customer is worth a lot over three years, but if you have to wait two years to recover what you spent, you need a lot of money in the bank to grow. Bootstrapped companies in particular live or die on payback: they can only reinvest cash that has already come back.
Payback is also more robust than LTV early on. It depends on months of data you actually have, not on long-term churn assumptions. That makes it a more honest metric for young startups.
Upfront payment changes the picture. Annual plans paid in advance can bring payback to zero or near it, because you collect a year of revenue immediately. That's one reason many startups offer an annual discount. Channels with long-lived assets, like SEO content and permanent listings, also improve payback over time as the same spend keeps bringing customers.
Track it by channel and by plan. A channel with slightly higher CAC but much faster payback, because it brings annual-plan buyers, may be the better one to grow.
Why it matters for founders
Payback tells you how fast your growth pays for itself. For a founder funding growth from revenue, it's often the single most important acquisition number.
Example
Paid ads bring customers at $400 CAC on monthly plans, a 10-month payback. Launch and directory listings bring customers at $120 CAC, many on annual plans, paying back in under two months.
Common mistakes
- Using revenue instead of gross margin in the calculation.
- Ignoring the effect of annual prepayment.
- Comparing payback across channels measured over different periods.
Related terms
- Customer acquisition cost (CAC)Customer acquisition cost (CAC) is the total sales and marketing spend in a period divided by the number of new customers won in that period. It tells you what it costs, on average, to get one paying customer.
- Customer lifetime value (LTV)Customer lifetime value (LTV) is an estimate of the total gross profit a business will earn from a typical customer over the whole time they stay a customer. It's compared with CAC to judge whether acquisition is worth it.
- Monthly recurring revenue (MRR)Monthly recurring revenue (MRR) is the normalized amount of subscription revenue a business expects to receive every month from its active customers, excluding one-time fees and usage that isn't committed.
- Churn rateChurn rate is the percentage of customers, or of recurring revenue, lost during a period. Monthly customer churn is customers who cancelled this month divided by customers you had at the start of the month.