When a publisher spends money to acquire a user, that spend is not recovered instantly. The user earns it back gradually, through ad revenue and purchases, day after day. Payback period measures how long that takes: the number of days before a user or cohort has generated enough revenue to cover what it cost to bring them in. Until that point, the acquisition is running at a loss on paper.
How to calculate payback period
The rough version divides acquisition cost by daily revenue per user:
CAC is the cost to acquire one user, and ARPDAU is the average revenue that user generates per active day. Dividing one by the other gives the number of active days needed to break even.
A worked example
Say it costs $30 to acquire a user, and each active user earns an average of $0.30 a day:
That user takes 100 active days to pay back their acquisition cost. If a change to monetization lifts ARPDAU to $0.40, the same $30 CAC now pays back in 75 days:
Nothing about the acquisition cost changed, yet the money comes back 25 days sooner, purely because each active day earns more.
Why payback period matters
Payback period governs how fast a publisher can grow. Cash spent on acquisition is tied up until it is recovered, so a shorter payback means the same budget recycles into new users more times per year. It sits alongside LTV and return on ad spend: LTV tells you whether a user is profitable at all over their lifetime, while payback tells you how quickly you get your money back to spend again. A user can be highly profitable in the long run yet still strain cash flow if the payback stretches over many months. Finance teams watch it closely, because a business that recovers its spend in weeks can grow on its own cash, while one that waits months needs far more working capital to fund the same growth.
How the offerwall shortens payback
Payback shortens whenever daily revenue per user rises, since ARPDAU is the denominator in the formula. An offerwall adds a high-value revenue stream on top of existing ads: engaged users complete offers for currency, and those completions lift the average revenue each active user generates per day. A higher ARPDAU pulls the payback period down directly. For a publisher, that means acquisition cost is recovered sooner, and a faster payback makes it safer to scale spending on new users.
Common mistakes to avoid
Confusing payback period with LTV. Payback measures how fast you recover CAC, while LTV measures total value over a user's lifetime.
Using a blended ARPDAU across very different cohorts, which hides the fact that some channels pay back quickly and others never do.
Ignoring retention. The formula assumes users stay active, so if they churn before payback, the real recovery takes longer or never arrives.
Frequently asked questions
Q: How do you calculate payback period?
Q: What is a good payback period?
Q: How is payback period different from LTV?
Keep reading
Metric
CAC (Customer Acquisition Cost) is the total cost of acquiring one paying customer, found by dividing acquisition spend by the number of new customers gained. It tells a publisher whether growth is profitable, and it only works when it stays well below the value each customer returns.
Metric
ARPDAU measures how much revenue an app generates, on average, from each active user in a single day. It's one of the most-watched monetization metrics in mobile gaming and apps because it blends how well you monetize with how engaged your users are into a single daily number.
Metric
LTV (Lifetime Value) is the total revenue you expect from a user across their entire relationship with your app. It sets the ceiling on what you can profitably spend to acquire that user.
Ad Format
An offerwall is an in-app ad unit that shows users a list of offers, such as surveys, sign-ups, purchases, or gameplay tasks, that they can complete in exchange for virtual currency or rewards. Because users opt in and choose their own offers, offerwalls are one of the least intrusive and highest-earning monetization formats in mobile.