What is CPI (Cost Per Install)?

CPI (Cost Per Install) is the cost of one mobile app install. Standard user acquisition metric in in-app networks, Google UAC, Meta app campaigns, and TikTok app ads.

Formula

CPI = Ad spend ÷ Installs. Installs must be attributed by MMP or store (SKAdNetwork on iOS with delay and aggregated data).

After install

Buyers track CPI → signup/deposit/subscription CR → LTV and ROAS. Optimizing CPI alone without events attracts incentivized and low-quality installs.

CPI vs CPA

CPA on in-app events (deposit, purchase) is stricter for gambling and fintech apps. CPI is simpler for top-of-funnel scale.

Risks

Install fraud, SDK spoofing, duplicate devices. SKAdNetwork limits granular postbacks—sub_id and creative stats are reduced. MMP holds and fraud checks are mandatory.

See also: mobile apps vertical, in-app ads, install fraud, SKAdNetwork.