What is CAC payback period and why does it matter?

CAC payback period is how long it takes to recover the cost of acquiring a customer through their purchases. If you spend $100 to acquire a customer who generates $25/month in contribution margin, your payback is 4 months. Investors care because shorter payback = faster reinvestment = faster growth. A payback over 12 months is a red flag for most investors.

What's the difference between nCAC and bCAC?

bCAC (Blended CAC) = Total ad spend ÷ Total customers acquired. nCAC (New Customer CAC) = Spend on new customers ÷ New customers only. The difference matters because returning customers are much cheaper to convert. Your blended CAC might look healthy at $45, but if nCAC is $78 and bCAC is $12, you're actually paying $78 to acquire each truly new customer.

How do I calculate contribution margin for CAC payback?

Contribution Margin = Revenue - Variable Costs (COGS + Shipping + Payment fees + Returns). Don't use revenue or gross margin — use contribution margin. If your AOV is $100 but COGS is $40, shipping is $8, payment fees are $3, and returns are $5, your contribution margin is $44. That's what actually pays back your CAC.

What's a good CAC payback period?

For DTC/ecommerce: Under 6 months is excellent, 6-12 months is acceptable, over 12 months is concerning. For SaaS: Under 12 months is good, 12-18 months is acceptable, over 18 months needs attention. These benchmarks assume you have strong retention — if customers churn before payback, you lose money on every acquisition.

How does repeat purchase rate affect CAC payback?

Dramatically. A customer who buys once provides one contribution margin payment toward CAC recovery. A customer who buys 3x/year provides 3x the payback velocity. Our calculator models scenarios: 'At 25% repeat rate, payback is 8 months. At 40% repeat rate, payback drops to 5 months.' This shows where to focus — sometimes improving retention beats lowering CAC.

Why is my CAC payback getting worse?

Common causes: 1) Rising CPMs increasing acquisition costs, 2) Lower AOV from discounting, 3) Higher COGS/shipping eating into margin, 4) Worse customer quality (lower repeat rates), 5) Attribution issues making CAC appear lower than reality. Max analyzes your inputs to identify which factor is hurting you most.

How do I present CAC payback to investors?

Show: 1) Blended CAC AND nCAC separately — investors know to ask, 2) Contribution margin breakdown — proves you understand unit economics, 3) Payback by cohort — shows if you're improving, 4) LTV:CAC ratio — should be 3:1 or better, 5) Cash flow impact — how much capital you need to grow. Our calculator generates a board-ready PDF with all of this.

CAC payback calculator

Enter your unit economics. Get true CAC payback with nCAC vs bCAC separation and cash crisis warnings.

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What is Contribution Margin?

Revenue minus COGS, shipping, returns, and payment fees. If your $100 order has $30 COGS, $8 shipping, $5 returns, and $3 fees, your contribution margin is 54%.