Effective cost per install (eCPI)
Acquisition metric. How do users find and install the app?
What is effective cost per install?
Effective cost per install (eCPI) is the cost per install worked out after the fact, by dividing what a campaign cost by the installs it delivered, whatever the buying model.
CPM: cost per mille: the price of 1,000 ad impressions.
CPC: cost per click: the price paid each time someone clicks the ad.
How to calculate eCPI
eCPI = Total cost ÷ Installs- Total cost
- what the campaign cost, whether bought per impression (CPM), per click (CPC) or per install
- Installs
- the installs the campaign delivered; some teams use all installs, organic included
Where definitions differ
| Variant | Formula | When to use it |
|---|---|---|
| eCPI on a non-CPI buy | (Impressions ÷ 1,000 × CPM) ÷ Installs | Turns a CPM or CPC campaign into a cost per install so it can be compared with CPI-priced buys. |
| Blended eCPI | Total spend ÷ All installs, organic included | Some teams use eCPI to mean this. It falls as organic installs rise, even if paid efficiency is unchanged. |
eCPI calculator
Example inputs: change them to your own numbers. The examples only make the calculator show a worked answer; they are not benchmarks or targets. Runs in your browser; nothing you type is sent anywhere.
- Campaign cost
- $12,000
- eCPI (campaign installs)
- $2
- Blended eCPI (all installs)
- $1.20
Why is eCPI lower than CPI?
When eCPI is worked out across all installs, organic installs add to the divisor but not to the cost, so it comes out lower than paid CPI. On a single paid campaign, eCPI and CPI are the same number.
How eCPI differs by vertical
| EdTech | Useful when brand video or creator deals are bought on reach rather than installs. |
|---|---|
| Fintech | Turns CPM-bought brand campaigns into a cost per install, before KYC drop-off is added. |
| OTT and streaming | Common for CPM-heavy launch campaigns around a new title or season. |
| Gaming | The standard way to compare CPM and CPI buys across ad networks. |
Common mistakes
- Using blended eCPI to judge one channel's efficiency.
- Comparing eCPI from different periods without the same organic baseline.
Questions
What does eCPI stand for?
Effective cost per install. It is the cost per install you work out after a campaign has run, whatever you were billed for.
How do you calculate eCPI from CPM?
Multiply impressions by the CPM and divide by 1,000 to get the cost, then divide the cost by installs. 2M impressions at a $6 CPM cost $12k; with 6k installs that is an eCPI of $2.
Is eCPI the same as blended CPI?
Sometimes. Some teams use eCPI for one campaign's effective cost and others for total spend divided by all installs. Say which one you mean in reports.
Which currency do the calculators use?
The calculators show US dollars, but every formula works in any currency: enter your own figures in the currency you report in and read the results in that currency.
What is the difference between a metric and a KPI?
A metric is any measured quantity; a KPI is a metric a team has chosen as a target for judging performance. Most metrics here become KPIs only for the teams whose work moves them.
Do I need an MMP to measure these metrics?
Not for all of them. Engagement and monetisation metrics come from product analytics and billing data, while metrics split by ad channel, such as CPI, ROAS or retention by source, need installs attributed to campaigns.