What Is CPI? Cost Per Install Explained

What CPI means

CPI, or cost per install, is what you pay on average for one new install of your mobile app or game. It is the main price that app developers watch when they buy users, and many ad networks sell app campaigns directly on a CPI basis, charging only when an install happens.

CPI can describe two things: the pricing model, where you pay a fixed price for each install, and the metric, where you divide what you spent by the installs you got, whatever pricing model you used.

The CPI formula

CPI = ad spend ÷ new installs. If you spend $500 and get 1,250 installs, your CPI is $0.40.

When you buy on a different model, the same formula tells you what installs really cost. With CPM pricing, CPI = CPM ÷ (1,000 × install rate per impression). With CPC pricing, CPI = CPC ÷ install rate per click.

What counts as an install

Most platforms count an install when the app is opened for the first time, not when it is downloaded. The open must usually happen within an attribution window after the click, often a few days, and the device must not have had the app before. Reinstalls, updates, and installs from users who never clicked your ad normally do not count. Check how your network defines an install before you compare prices.

What drives CPI

• Country. Installs cost the most in high-income markets such as the United States and the least in large, lower-income markets. See Tier 1, 2 and 3 countries explained.
• Platform. iOS installs usually cost more than Android installs in the same country, partly because iPhone users tend to spend more in apps.
• Category. Games, finance, and shopping apps compete with many advertisers. Niche utilities often pay less.
• Season. Prices usually rise in the weeks before the end-of-year holidays, when retailers flood every channel.
• Creative and store page. Better ads bring more clicks, and a better store page turns more clicks into installs.
• Incentive. Installs from users who receive a reward are cheaper and faster, but they need a strong first experience to stay.

CPI vs CPA vs CPE

The deeper the event, the higher the price per result, but the more of that price goes to users who matter. Many developers start with CPI to get volume and move to CPE or CPA once they know which events predict revenue. CPM vs CPC vs CPA covers the wider comparison.

How much can you pay per install?

Work backwards from what an install earns you. Estimate the revenue an average new user brings over a period you trust, such as 90 days, from purchases, subscriptions, and ads. That is the value of one install. Then decide how much return you want on each dollar you spend.

Maximum CPI = value of one install ÷ target ROAS.

See What is ROAS? and CAC vs CPA vs LTV for the reasoning behind these numbers.

Judge installs by what happens next

A cheap install that is deleted the same day is expensive. Compare sources with these numbers instead of CPI alone:

• Day 1, day 7, and day 30 retention: the share of users who open the app again after one day, a week, and a month.
• Tutorial or onboarding completion: how many users reach the first real use of the app.
• Revenue per install after 7 and 30 days.
• Cost per retained user: spend divided by users still active on day 7. It often ranks sources differently from CPI.

Install fraud to watch for

Because installs are paid per result, they attract fraud. The most common types are device farms, where racks of phones install apps again and again, click spamming, where fake clicks claim credit for installs that would have happened anyway, and fake devices that simulate installs without a real phone. Warning signs include installs that never open the app a second time, many installs from the same few networks or device models, and installs that arrive seconds after a click. Ad fraud and bot traffic explains how to spot them.

How to lower CPI

1. Improve the store page. Clear screenshots, a short video, and a strong first line raise the install rate for every source.
2. Test creatives often. Ads wear out. Replace the weakest ones every couple of weeks.
3. Target where value is high but prices are lower. Countries just below the top tier often bring good users at a fraction of the price.
4. Pay for a deeper event. A higher price per result can still cost less per retained user.

Paying per install on Sharklio

On Sharklio, a task campaign can ask users to install your app and reach a first goal, such as finishing the tutorial or reaching level 5, and to send a screenshot as proof. You pay only for completions you approve, with a separate bid per country, and you can limit the campaign to Android or iOS and to mobile devices. That makes it a pay-per-engagement campaign rather than a simple pay-per-install one. Sharklio is launching soon. From the user’s side, Shark Earnings explains app offers in How to earn money downloading apps.

Frequently asked questions