CAC Payback Window
The number of months until a new customer's contribution margin equals the cost to acquire them.
CAC payback window is the time — in months — it takes for the contribution margin from a newly-acquired customer to equal the cost of acquiring them. Shorter is better: capital comes back faster and can be redeployed.
Context
CAC payback is a more honest capital-efficiency metric than LTV:CAC ratio because it doesn't rely on LTV assumptions about customers who haven't churned yet. Under 12 months is best-in-class for SaaS; under 6 months for DTC with repeat purchase; under 18 months for complex B2B.
For any business over 24 months CAC payback, you're effectively betting the company on LTV assumptions you can't validate until well after the capital is spent. Capital markets punish this.
A SaaS company with $600 blended CAC and $100/month gross margin per customer has a 6-month CAC payback — the top quartile of growth-stage SaaS and considered very healthy.
CAC payback is best tracked by cohort. Aggregate CAC payback obscures whether the picture is getting better or worse over time. A cohort-level view reveals whether recent CAC efficiency is stable, improving, or degrading.
Related terms
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More Paid Media terms
MER (Marketing Efficiency Ratio)
Total revenue divided by total marketing spend — a blended metric that resists attribution gaming.
CPM (Cost per Mille)
Cost per 1,000 impressions — the core pricing unit for paid media.
CPC (Cost per Click)
The cost of a single click on a paid advertisement.
CPA (Cost per Action/Acquisition)
The average ad cost per conversion event — the core paid efficiency metric.