CPI (Cost Per Install)

Cost per install (CPI) is the price paid for each attributed app install. It can be a pricing model — the advertiser pays a fixed amount per install — or a reporting metric calculated as spend divided by installs.

CPI is the most familiar mobile user acquisition metric, but it only describes the cost of the first step. Two campaigns with the same CPI can produce users with very different retention and revenue. That is why experienced UA teams pair CPI with quality guardrails such as D1 and D7 retention, or move to CPA and ROAS goals once enough post-install data exists. CPI levels vary widely by country, platform, app category and season, so benchmarks are only meaningful when they compare like with like.

When you set a CPI target, define it per market and platform, and review it together with the retention and revenue of the users it buys — that keeps the target honest as the campaign scales.