Payback Period (CAC Payback)

Payback period measures how long it takes to recoup the cost of acquiring a customer. The formula is: Payback Period = CAC / Monthly Contribution Margin per Customer. If you spend $60 to acquire a customer who generates $20/month in contribution margin, your payback period is 3 months.

For subscription e-commerce, payback period is arguably more important than the LTV:CAC ratio because it directly impacts cash flow. A 3:1 LTV:CAC ratio with a 12-month payback means you are funding 12 months of customer acquisition before seeing a return — which requires significant working capital. The same 3:1 ratio with a 3-month payback lets you reinvest profits into growth much faster.

Benchmark payback periods for e-commerce: under 3 months is excellent (you can scale aggressively), 3-6 months is healthy (sustainable growth), 6-12 months requires careful cash management, and over 12 months is a warning sign unless you have significant funding and high confidence in long-term retention.

The payback period varies dramatically by acquisition channel, which is why channel-level analysis matters. Your Meta Ads customers might have a 4-month payback while your Google Search customers pay back in 2 months. Organic and referral customers often have near-zero payback because the acquisition cost is minimal.

To shorten payback period, focus on: increasing average order value (AOV) in the first purchase, reducing variable costs (negotiate shipping, optimize COGS), accelerating time to second purchase through post-purchase campaigns, and shifting acquisition spend toward channels with faster payback even if the CAC is slightly higher.