Payback Period: How Fast You Recover CAC

In one line

Payback period is how long it takes the revenue from one user to repay the CAC you spent acquiring them.

What LTV:CAC cannot tell you

LTV:CAC is a ratio, and ratios have no time axis. A 3:1 result says the money comes back threefold — not whether that takes three months or three years.

For a growing business the difference is decisive. Slow recovery means that however good the ratio looks, cash drains while you keep pre-paying for acquisition. How fast you can scale spend is governed by payback period, not by the ratio.

Calculating it carefully

Read it from cumulative ARPU by cohort. Computing it on a blended average distorts the value whenever new-user volume shifts.

And recent cohorts that have not reached the crossing point require extrapolating the curve — that is a forecast, not a measurement, and the report should say so.

Go deeper

Ratio pitfalls are covered in LTV:CAC ratio and cohort curves in cohort analysis.

Frequently asked questions

LTV:CAC looks healthy but cash is tight — why?

LTV:CAC is a ratio with no time axis, so it says nothing about recovery speed. A 3:1 ratio that takes 18 months to repay still drains cash the whole time, because spend keeps going out.

How do I calculate payback period?

Plot cumulative ARPU by cohort and find where it crosses CAC. Cohorts that have not yet reached that point require extrapolation, so label those as estimates rather than observations.