CPI

Detailed explanation

CPI, or Cost Per Install, is a mobile-specific pricing and performance metric that measures the average cost of getting one user to install an app as a result of an advertising campaign. It is calculated by dividing total campaign spend by the number of resulting installs, and it is one of the most commonly used benchmarks in app marketing because installs are the first hard conversion event in a mobile funnel.

CPI alone, however, says nothing about what happens after installation — whether the user opens the app again, completes onboarding, or ever makes a purchase. A campaign with a low CPI but poor post-install retention or in-app conversion can be far less valuable than a campaign with a higher CPI that attracts users who stick around and spend. For this reason, app marketers increasingly weigh CPI against downstream metrics like retention rate, cost per in-app action, and return on ad spend from in-app purchases.

CPI benchmarks also vary substantially by platform, geography, app category, and seasonality, so it is generally more useful as a comparison across an advertiser's own campaigns and channels than as an absolute target borrowed from industry-wide averages.