What is Cost Per Install (CPI)?

Cost Per Install (CPI) is the amount of money you spend to get one new app install through paid advertising.

For example, if you spend $2,000 on a campaign and get 1,000 installs, your CPI is $2. It’s one of the most basic — and widely used — metrics in mobile user acquisition.

How does it work?

The formula is straightforward:

CPI = Total ad spend ÷ Number of installs

CPI can vary significantly based on:

• Country
  
  

• Platform (iOS vs Android)
  
  

• Ad network (Meta, Google, TikTok, etc.)
  
  

• Audience targeting
  
  

• Creative performance
  
  

• Auction competition
  
  

While CPI tells you how efficiently you're driving installs, it doesn’t say anything about quality — some users may never open the app or take any meaningful action after installing.

That’s why it’s often paired with deeper metrics like CPA, ARPU, or Retention Rate to understand true value.

Why it matters

CPI is a starting point for measuring paid acquisition performance.

It helps UA teams:

• Set benchmarks and budgets
  
  

• Compare acquisition costs across channels
  
  

• Monitor campaign efficiency
  
  

• Optimize creatives and targeting
  
  

However, optimizing only for low CPI can be misleading. A campaign that brings in cheap installs but no paying users isn’t truly efficient.

In short: CPI gets people in the door — but it’s what happens after the install that matters.