CAC payback period is the number of months it takes to earn back what you spent acquiring a customer. You calculate it by dividing CAC by the monthly gross profit that customer generates. A shorter payback period means cash returns faster and growth needs less funding.

This is the metric that decides whether you can self-fund growth. A 6-month payback means every customer pays you back twice a year and frees cash to acquire the next one. An 18-month payback means you are financing growth out of pocket for a year and a half before you break even. It governs how fast you can spend.

Example:

CAC is $6,000. The customer pays $2,000 per month at 50% gross margin, so $1,000 monthly gross profit. Payback period is $6,000 / $1,000 = 6 months.

What is a good CAC payback period?

For most B2B SaaS and services businesses, under 12 months is healthy and under 6 months is strong. Longer than 18 months strains cash flow.

Why use gross profit instead of revenue?

Revenue overstates what you actually keep. Gross profit reflects the real cash a customer contributes after delivery costs, which is what funds your next acquisition.