Payback Period Calculator

What is customer acquisition payback period?

CAC payback period estimates how long one customer's contribution takes to recover the cost of acquiring that customer. It connects acquisition efficiency with cash flow: the longer recovery takes, the longer acquisition spending remains tied up before it can fund more growth.

Payback period formula

Use payback months = CAC ÷ monthly customer contribution. Monthly contribution is usually monthly recurring revenue multiplied by gross margin, minus other variable customer costs that are not already included in cost of service.

If CAC is $600, monthly revenue is $120, and gross margin is 80%, monthly gross profit is $96. With no additional variable cost, estimated payback is 6.25 months.

Choose cohort-consistent inputs

• Calculate CAC and monthly contribution for the same customer cohort and acquisition period.
• Use recognized revenue and margin rules that match your financial reporting.
• Separate channels when acquisition cost or customer quality differs materially.
• Do not subtract the same cost through both gross margin and the extra variable-cost field.

What the simple model leaves out

A single-period estimate does not model churn, annual prepayments, delayed implementation, expansion revenue, or the time value of money. Use it as a fast diagnostic, then build a cohort cash-flow model when those effects are material to a budget or hiring decision.