Payback period
Also: CAC payback
Payback period is the number of days until a cohort's cumulative revenue equals the spend that acquired it — the point where cohort ROAS crosses 1.0x. It is the most decision-useful way to express LTV against CAC.
Payback = first day n where cumulative cohort revenue (Dn) ≥ acquisition spend
Payback turns a ratio into a cash question: how long is money out the door before it comes back? A channel that pays back in 45 days can be scaled aggressively; one that pays back in 300 days needs financing, however good its D365 LTV looks.
Compute it on proceeds (after store commission), not gross revenue, or the payback day will be optimistic by a third.
Related terms
In Roasy
Roasy computes this across every ad network, Adjust, and RevenueCat on one screen — real revenue, cohort windows, and the same definition everywhere.