eCPM means effective cost per mille: the revenue an ad or campaign earns per 1,000 impressions, whatever it was actually paid on. The M comes from the Latin mille, a thousand. Ad servers such as OpenX calculate it automatically, but every publisher should know how.
Worked example: a CPC campaign
A campaign paid per click is shown 2 million times in one day. The ad server counts 5,000 clicks, and the CPC rate is $0.50.
- Revenue: 5,000 clicks × $0.50 = $2,500
- Blocks of 1,000 impressions: 2,000,000 ÷ 1,000 = 2,000
- eCPM: $2,500 ÷ 2,000 = $1.25
Worked example: a CPA campaign
- Multiply the number of conversions by the CPA rate to get total revenue.
- Divide impressions by 1,000 to get the number of blocks.
- Divide revenue by the number of blocks.
Suppose a casino affiliate banner is shown 400,000 times and brings 12 first-time depositors at a $150 CPA. Revenue is $1,800, there are 400 blocks of 1,000 impressions, so the eCPM is $4.50, well above most display networks. The same banner with 3 depositors would earn an eCPM of $1.13. That volatility is why gambling publishers compare CPA, revenue share and flat CPM deals in eCPM terms. More in revenue share vs CPA.
| CPM | Price paid per 1,000 impressions |
|---|---|
| CPC | Price paid per click |
| CPA | Price paid per action, such as a sign-up or first deposit |
| eCPM | Any of the above converted to revenue per 1,000 impressions |
Related: full OpenX review, how to calculate an average CPM rate.
