Effective cost per thousand impressions (technically, “effective cost per mille”).
eCPM helps compare media with different pricing methods by converting everything to a common metric. This can be helpful when you have a mix of ad buys denominated in cost per impression, cost per click, cost per lead, cost per action, fixed-price sponsorship, or other pricing methods. Sometimes, eCPM is used to refer to revenue per thousand impressions on the publisher’s side.
As long as you have information for cost and impressions, you can calculate eCPM.
eCPM = (total cost/impressions) * 1000
eCPM = total cost / (impressions / 1,000)
eCPM = (CPC * clicks) / (impressions / 1,000)
eCPM = (CPL * leads) / (impressions / 1,000)