See how many months of gross margin it takes to earn back what you spend to win a customer — and where the recovery curve crosses break-even.
Gross margin is revenue minus cost of goods (hosting, support, payment fees) — only that slice repays CAC.
Payback period
12.5mo
Gross margin / month
$96
Acceptable
CAC recovered over 24 months
Payback is one number on a blended average. It hides which channels actually pay back, and ignores expansion and churn after break-even. Pair it with churn and LTV for the real shape.
Blended CAC lies. One average hides a 3-month channel and an 18-month channel. Split CAC by where customers came from before you trust the number.
Margin isn't a guess. When revenue and cost-to-serve sit on one spine, gross margin per account is measured, not assumed.
Payback meets retention. A short payback means nothing if those customers churn at month 7 — read it next to your churn curve, not alone.
FAQ
CAC payback questions
What is the CAC payback period?
CAC payback is the number of months of gross-margin revenue from a customer needed to repay what it cost to acquire them. CAC payback = CAC ÷ (ARPA × gross margin). For example, $1,200 CAC ÷ ($120 × 80%) ≈ 12.5 months.
What is a good CAC payback period?
A common SaaS rule of thumb is under 12 months is healthy, 12–18 is acceptable for higher-ACV or longer sales cycles, and over 18 months strains cash flow because you're financing growth for longer. Lower is better, but it always trades off against growth rate.
Why divide by gross margin instead of revenue?
Only the gross-margin portion of a customer's revenue actually goes toward repaying acquisition cost — the rest covers cost of goods (hosting, support, payment fees). Dividing by raw revenue overstates how fast you recover CAC; using gross margin is the honest version.
What does CAC payback miss?
A single blended CAC hides big differences between channels, and payback says nothing about what happens after you recover the cost — expansion revenue shortens effective payback while churn lengthens it. Pair it with churn and LTV for the full picture.