Payback Period: The Metric That Governs UA Spend
ROAS and LTV matter, but payback period decides how fast you can scale without running out of cash. The most underrated UA metric.
Key takeaways
- Payback period is how long it takes a cohort's revenue to repay its acquisition cost.
- It governs cash and scale: shorter payback lets you reinvest and grow faster.
Teams obsess over CAC, LTV and ROAS, then forget the metric that actually limits growth: how long until the money comes back. Payback period is the quiet constraint on how fast you can scale.
How to calculate it
Take a cohort's acquisition cost and divide by the contribution it generates per period, then find the month its cumulative revenue repays its CAC. That crossover point is your payback period.
What a healthy window looks like
There is no universal number; it depends on your margins and cash. Many subscription apps aim for payback inside three to twelve months. The right target is whatever your balance sheet can fund while you wait.
Why it limits scale
Growth is a cash-recycling engine: the faster cohorts repay, the faster you can reinvest into the next ones. Long payback throttles that loop even when LTV looks great, because the cash is locked up while you wait for it.
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