Definition:
Cost per install (CPI) is the amount an advertiser pays each time a user installs their mobile app as a direct result of an ad. It is one of the most widely used pricing and performance metrics in mobile app marketing, giving you a clear measure of how efficiently your ad spend is converting into new users.
Formula:
CPI = Total Ad Spend ÷ Total Installs
What Is Cost Per Install?
CPI is both a pricing model and a performance metric. As a pricing model, it means you are charged by an ad network only when a user installs your app, typically after clicking on an ad and opening the app for the first time. As a performance metric, it tells you how much each new user is costing you across your campaigns.
That dual role makes CPI one of the most practical numbers in mobile marketing. It connects your spend directly to a concrete outcome like an install, rather than a softer signal like a click or an impression.
The CPI Formula
The calculation is straightforward:
Formula:
Average CPI ($) = Total Ad Spend ÷ Total Installs
例:
If you spent $10,000 on a campaign that generated 5,000 installs:
CPI = $10,000 ÷ 5,000 = $2.00
Your average CPI for that campaign is $2.00.
In Tenjin, you will see two CPI metrics reported:
| メトリック | Formula |
| CPI | Total Ad Spend ÷ Total Reported Installs |
| tCPI | Total Ad Spend ÷ Total Tracked Installs |
The difference between the two mirrors the distinction between reported and tracked data. Reported installs come from the ad network; tracked installs are recorded independently by Tenjin. Comparing both gives you a more complete and accurate picture of your true acquisition cost.
What Affects Your CPI?
CPI is not a fixed number. It shifts based on a range of factors, some within your control and some not.
プラットフォーム
iOS and Android campaigns typically produce different CPIs. iOS has historically commanded higher CPIs due to its audience profile and the impact of ATT on targeting precision.
Geography
Acquiring users in tier-one markets like the US, UK, or Australia costs significantly more than in lower-competition regions. Country-level CPI variation can be substantial.
Ad Network and Channel
Different networks have different inventory, auction dynamics, and audience quality. CPI varies across channels even for the same app and creative.
Audience Targeting
Narrower, more competitive audiences tend to cost more to reach. Broader targeting may lower CPI but bring in users with lower downstream value.
Creative Performance
Ad creative has a direct impact on click-through and conversion rates, which flow through to your CPI. A strong creative lowers your effective cost per install.
App Store Listing Quality (ASO)
Even after a user clicks your ad, they need to convert on your store page. A well-optimized listing with clear screenshots, strong reviews, a compelling description improves that conversion rate and brings your CPI down.
Why CPI Matters
CPI is one of the primary ways growth teams evaluate the efficiency of their user acquisition efforts. Here is where it earns its place:
Budget Efficiency
Tracking CPI across campaigns and channels shows you where you are getting the most installs for your spend and where you are overpaying.
Channel Comparison
CPI lets you compare the cost of acquiring users across different networks, creatives, and targeting strategies on a like-for-like basis.
App Store Visibility
Install volume is a factor in app store ranking algorithms. Understanding which campaigns drive installs most efficiently helps you invest in visibility as well as growth.
Monetization Planning
CPI is the acquisition side of the equation. To understand whether your spend is sustainable, you need to compare it against the revenue each user generates, which is where LTV comes in.
CPI and User Quality
A low CPI is not always a good CPI. If a campaign delivers installs cheaply but those users churn immediately, never engage, and generate no revenue, the low CPI is misleading.
This is one of the most important things to understand about CPI as a metric: it measures the cost of an install, not the value of a user. A campaign with a higher CPI that brings in users with strong retention and high lifetime value will often outperform a cheaper campaign on every metric that actually matters.
The most effective way to evaluate CPI is alongside downstream performance data like retention rates, engagement, in-app revenue, and LTV. That fuller picture tells you whether you are acquiring users efficiently or just cheaply.
What Is a Good CPI?
CPI benchmarks vary widely depending on platform, country, app category, and monetization model. There is no universal number that counts as good or bad.
Tenjin publishes regular benchmark reports that give you real-world CPI data across app categories and markets. This allows you to see how your numbers compare and make more informed decisions about where and how to spend.
How to Improve Your CPI
Test and Iterate on Creatives
Ad creative is one of the most direct levers you have on CPI. Regular testing across formats, messages, and visuals helps you find what drives the highest conversion rates at the lowest cost.
Refine Your Targeting
Reaching the right audience reduces wasted spend. Use performance data to identify the user segments that convert efficiently and focus your budget there.
Optimize Your App Store Listing
Your store page is where the click becomes an install. Improving screenshots, previews, ratings, and copy directly improves your install conversion rate — and your CPI.
Compare CPI and tCPI
Monitoring both reported and tracked installs in Tenjin helps you catch discrepancies early and ensure your acquisition cost data is accurate.
Look Beyond the Install
Pair CPI with retention and LTV data to make sure you are not just optimizing for cheap installs at the expense of user quality.