What is cost per install (CPI)?

Cost per install (CPI) is how much you pay for each app install, making it more relevant to app campaigns. In the context of e-commerce businesses using Catalog Ads, CPI specifically tracks the cost incurred each time a user installs the brand’s mobile app after engaging with one of their ads. 

How do you calculate CPI?

To work out your CPI, you divide your total ad spend by your total number of app installs. 

For example, if you spent $1,000 on ads that generated 20 app installs, your CPI is $50.   

Why is CPI important in e-commerce?

Mobile apps have become a valuable tool for driving customer loyalty and repeat purchases. Tracking your CPI helps to evaluate the cost-effectiveness of ad campaigns focused on driving app downloads. It can also be used as justification to scale your mobile app, if you can forecast good growth and show predictable user acquisition costs.

Which factors can impact your CPI?

App store experience

If your app store listing has poor screenshots and bad reviews, you can expect fewer users to complete the app installation. This will drive up your CPI. 

Incentives

Ads aimed at encouraging app installs are often linked to messaging like “install and save” or “10% off your first in-app order”. These types of incentives can boost your CPI, but keep in mind that it cuts into your profitability after they’ve installed the app. 

Best practices in measuring CPI

Apply segmentation

Tracking the average CPI can be misleading. To get a more accurate understanding of the true costs, segment your CPI by channel (e.g. Meta, Google, etc.), region, and creative. This will help you to pinpoint what works, allowing you to optimise your ad spend accordingly.  

Analyse it in conjunction with post-install metrics

A low CPI means less if many users delete the app the next day. To ensure that you’re acquiring valuable users, combine CPI with other metrics like retention rate, cost per action (CPA), and lifetime value (LTV). 

Track it across all channels

One of the challenges of tracking your CPI is multi-touch attribution. Users may see an ad on one platform but install your mobile app only after searching for it organically. 

As such, it’s best to track it across all channels, e.g. paid ads, email campaigns, organic search, etc. This way, you’ll gain a more complete picture and avoid undervaluing cross-channel strategies.