CAC Payback Period Calculator
How many months until a new customer's gross margin repays what you spent acquiring them.
This free CAC payback calculator works out how many months it takes a new customer's gross margin to repay their acquisition cost. Enter your CAC, the monthly revenue a customer generates and your gross margin, and it returns the monthly margin contribution and the payback period.
Where LTV:CAC asks whether the economics work eventually, payback asks the sharper question: how long is your cash locked up in the meantime? Every dollar of CAC is spent today and recouped over the payback window — the longer the window, the more working capital growth consumes.
How to calculate CAC payback
Divide CAC by the monthly gross margin a customer generates: CAC ÷ (monthly revenue × gross margin %). Use margin, not revenue — the payback has to come out of what a customer actually contributes after the cost of serving them, so a 75% margin stretches the true payback a third beyond the naive revenue-based number.
Read the result against your retention: a payback longer than your average customer lifespan means many customers never pay back at all. High-NRR enterprise businesses can afford longer paybacks because customers keep growing after breakeven; high-churn SMB products cannot.
CAC payback (months) = CAC ÷ (monthly revenue per customer × gross margin %).
A $2,000 CAC recouped from a customer paying $200/month at 75% gross margin — $150 of monthly margin — pays back in $2,000 ÷ $150 ≈ 13.3 months. Strong for mid-market SaaS, though past 24 months growth is running on financing rather than economics.
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