SaaS & Retention

CAC Payback Period Calculator

Payback period is the metric that decides how fast you can grow without running out of cash. A great LTV to CAC ratio with a twenty-month payback will still starve a business that has to fund the gap.

Your numbers

Result

CAC payback period8.3 months
Monthly gross profit per customer$144.00
Gross profit in twelve months$1,728
First-year profit after CAC$528

FormulaCAC payback (months) = CAC ÷ (monthly revenue per customer × gross margin %)

Worked example

A $1,200 CAC against $180 of monthly revenue at 80 percent margin means $144 of monthly gross profit and an 8.3 month payback. Over twelve months that customer produces $1,728 of gross profit, leaving $528 after acquisition cost. Every month you shorten the payback is a month of cash you can redeploy into more acquisition.

What to watch for

Under 12 months is the usual health line for subscription businesses, and under 6 is genuinely strong. Above 18 months you need either patient capital or a very high retention rate, and preferably both.

Annual prepayment is the most underrated payback lever there is. Collecting twelve months upfront in exchange for a modest discount can take payback close to immediate, and it usually improves retention as a side effect.

Use gross profit rather than revenue in the denominator. Paying back CAC out of revenue you have not yet delivered against is how a business appears to be recovering acquisition cost while quietly losing money on every customer.

Frequently asked questions

What is a good CAC payback period?

Under 12 months is a common benchmark for small and mid-market subscription businesses. Enterprise deals with long contracts and low churn can justify longer paybacks, but only if the retention data genuinely supports it.

How do I shorten payback?

Push annual plans, raise prices, improve onboarding conversion so fewer acquired customers leave before they pay back, and cut acquisition channels with the highest CAC. Lowering CAC and increasing ARPU move the number by the same arithmetic, but ARPU is usually the easier lever.

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