What is eCPM and how is it calculated?

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Calculating eCPM for a CPM campaign
Calculating eCPM for a CPC campaign

The acronym eCPM means ‘effective cost per mille’. It is the outcome of a calculation of the ad revenue generated by a banner or campaign, divided by the number of ad impressions of that banner or campaign expressed in units of 1,000. The ‘M’ for mille in the name comes from the Latin meaning 1,000. The formula to calculate eCPM is not all that complicated, once you realize the components that go into the computation.

Calculating eCPM for a CPM campaign #

When the campaign has a rate expressed in CPM (cost per mille), there is not a lot that needs to be done. The CPM rate is by definition identical to the eCPM value of that campaign.

Calculating eCPM for a CPC campaign #

For campaigns with a CPC rate, the calculation works like this:

You will need to look up the number of ad impressions over a given period of time
You will also need to look up the number of clicks on these ads over the same period of time
And finally, you will need to know the CPC rate for the campaign

Once you know this input data, the formula is:

Multiply the number of clicks by the CPC rate to come up with total revenue
Divide the number of impressions by 1,000, giving you the number of blocks of 1,000 impressions delivered
Divide the total revenue by the number of blocks of 1,000 impressions to come up with the eCPM value

Let’s use the following fictional numbers for an example:

A campaign with a CPC pricing was displayed 2 million times in a period of 1 day
in that same day, the ad server counted 5,000 clicks on the banners of the campaign
the CPC rate for the campaign was set to US$ 0.50

We can now calculate the eCPM of this campaign with a CPC rate:

Total revenue was 5,000 clicks times $ 0.50 equals $ 2,500
2 million impressions are equal to 2,000 blocks of 1,000 impressions
The eCPM is $ 2,500 divided by 2,000, equals an eCPM of $ 1.25

In reality, you will probably never see nice round numbers like these, but if you use the formula explained above, it is simple to compute the eCPM value of a CPC campaign for any given time frame.