How eCPM is calculated
Effective cost per mille converts any ad result to a per-1,000-impressions figure:
eCPM = (ad earnings / impressions) x 1,000
A worked example: a casual game shows 2,000,000 ad impressions in a day across banners, interstitials and rewarded video, and earns $5,600. eCPM is 5,600 / 2,000,000 x 1,000 = $2.80.
The "effective" part matters because many impressions are not sold on a CPM basis. A network paying per click or per install still produces a revenue per impression once you divide by impressions served. eCPM puts all of them on one scale so a publisher can compare them.
Who uses eCPM
eCPM is mainly a publisher metric. Apps that sell ad space to advertisers use it to decide which ad networks get which impressions, to compare formats, and to set floors in mediation. A rewarded video network paying $12 eCPM and a banner network paying $0.40 eCPM tell you very different things about where to put ad placements.
Advertisers sometimes use eCPM the other way, as an effective cost: spend divided by impressions times 1,000, even when they bought clicks or installs. That helps compare a CPC campaign with a CPM one.
eCPM and revenue per user
For an ad-supported app, daily ad revenue per user follows from eCPM and impressions per user:
ad ARPDAU = eCPM x impressions per DAU / 1,000
If eCPM is $2.80 and the average daily user sees 15 ads, ad revenue per daily active user is 2.80 x 15 / 1,000 = $0.042. Raising impressions per user too far can hurt retention, so teams track eCPM, impressions per user and retention together.
eCPM and measurement
eCPM data comes from your ad monetization stack: the mediation platform and the networks that buy your inventory. Linkrunner does not import ad monetization revenue today. It attributes installs, in-app events, in-app purchases and subscription revenue to the campaigns that acquired each user, so for ad-supported apps you would join ad revenue from your mediation reports with Linkrunner's install and cohort data, for example through a raw data export or the reporting API.