CTR 

Click-through rate or CTR is a way of measuring the success of an online advertising campaign. A CTR is obtained by dividing the number of users who clicked on an ad on a web page by the number of times the ad was delivered (impressions). For example, if your banner ad was delivered 100 times (impressions delivered) and 1 person clicked on it (clicks recorded), then the resulting CTR would be 1%.

Banner ad click-through rates have fallen over time, often measuring significantly less than 1%. By selecting an appropriate advertising site with high affinity (e.g. a movie magazine for a movie advertisement), the same banner can achieve a substantially higher click-through rate. Personalized ads, unusual formats, and more obtrusive ads typically have higher click-through rates than standard banner ads.

CTR is most commonly defined as number of clicks divided by number of impressions and generally not in terms of number of persons who clicked. This is an important difference because if one person clicks 10 times on the same advertisement instead of once then the CTR would increase in the earlier definition but would stay the same in term of later definition.

CPM

CPM Cost Per Mille or cost ‰ or Cost per thousand or cost per mille (abbreviated as CPT or, more commonly, CPM). In Latin mille means thousand, therefore, CPM means cost per thousand. CPM is a commonly used measurement in advertising. Radio, television, newspaper, magazine and online advertising can be purchased on the basis of what it costs to show the ad to one thousand viewers (CPM). It is used in marketing as a benchmark to calculate the relative cost of an advertising campaign or an ad message in a given medium. Rather than an absolute cost, CPM estimates the cost per 1000 views of the ad.

Calculation

An example of computing the CPM:

1. Total cost for running the ad is $15,000.
2. The total audience is 2,400,000 people.
3. The CPM is computed as CPM = ($15,000 x 1000)/2,400,000 = $6.25
4. CPM can also be calculated as CPM = $15,000/(2,400,000/1000) = $6.25

The second equation is easier for solving for unknown Cost of Unit when you know Audience and desired CPM.

eCPM

Effective Cost Per Mille or eCPM (as it is often initialized to) is a phrase often used in online advertising and online marketing circles. It means the cost of every 1,000 ad impressions shown.

CPM is considered the optimal form of selling online advertising from the publisher's point of view. A publisher gets paid every time an ad is shown.

eCPM is used to measure the effectiveness of a publisher's inventory being sold (by the publisher) via a CPA, CPC, or CPT basis. In other words, the eCPM tells the publisher what they would have received if they sold the advertising inventory on a CPM basis (instead of a CPA, CPC, or CPT basis).