Cost-Per-Thousand vs. Cost-Per-Click vs. Cost-Per-Action

with No Comments

Cost-Per-Thousand vs. Cost-Per-Click vs. Cost-Per-Action

Cost per Click. Cost per Mille. Cost per Action. Cost per Lead. Cost per Engagement…

Today’s digital advertising is filled with many different pricing options and campaign metrics to monitor. The Cost-Per-Thousand (CPM), Cost-Per-Click (CPC), and Cost-Per-Action (CPA pricing choices and parameters have significant implications for advertisers’ budgeting strategy and campaign success. Knowing the basics of these metrics are important before diving into any digital advertising campaign strategy.

CPM—payment when an ad is seen

CPM (cost per mille or thousand impressions) is how all programmatic advertising is bought and sold. Under this pricing model, the publisher is paid every time a website visitor sees an ad. It’s commonly used where an advertiser wants a branding campaign; the focus is on raising consumer awareness of a company or product rather than persuading them to buy right now.

Example: a website that charges a CPM of $5 will earn $5 for every 1,000 ads that its visitors see.

CPC—payment when an ad is clicked

The interactive nature of websites allows advertisers to be more discerning about when they pay. Since the early days of the internet, the ‘click’ has been used as a measure of ad effectiveness, as it indicates their interest in a product or service. The percentage of website visitors who see an ad and click it is referred to as the click-through-rate or CTR and the website is paid a cost per click (CPC) for each click on an ad. Given the CPC of an ad and its CTR we can work our way back to a CPM (sometimes referred to as an estimated CPM or eCPM). This is useful if you want to compare the performance of ad networks that use different pricing models.

eCPM = CPC * CTR * 1,000 (because it relates to 1,000 ads)

For example, a website that charges a CPC of $2.50 where 15 in every 10,000 ads are clicked (CTR of 0.0015) will have an eCPM of $3.75

2.50 * 0.0015 * 1,000 = $3.75

CPA—payment when an action is carried out

Pricing models have moved beyond the click, and it is now common for the publisher to pay a cost per user action (CPA). In this pricing model, the website is only paid when a website visitor clicks through an ad and completes a purchase on the advertiser’s site. In comparison to CPC the CPA pricing model is another degree of separation away from CPM. We first estimate a CPC using the CPA and a conversion rate of clicks to actions which we call the Action Rate (AR). The AR is the percentage of visitors to the advertiser’s site who go on to complete the Action.


For example consider an advertiser who pays $10 per action (CPA) and 10% of visitors carry out the action (AR). This equates the an estimated cost per click of $1.

10 * 0.1 = $1

We can take this eCPC and convert it to an eCPM the same way as we did above. Let’s assume the same rate of 15 in every 10,000 visitors clicks on the ad (CTR 0.0015). This yields an eCPM of $1.50

1.00 * 0.0015 * 1,000 = $1.50