Click-through rate (CTR) is a key health metric in digital marketing. It is used to identify the ad creative which is driving the best ratio of clicks to impressions.

Cost per action (CPA) is a key marking metric used to show the performance of marketing activity showing the amount it costs to get a customer to take the desired action. It is calculated by dividing the total cost by the number of times the desired action was taken by the customer.

Cost per click (CPC) is a key marking metric used to show the performance of marketing activity by showing the cost it takes to generate a click. It is calculated by dividing the total cost by the number of clicks.

Cost per target audience rating point (TARP) is a marketing metric used to show the cost per percentage of the specific target audience and is a metric most commonly used to measure the cost of television advertising. CPT is calculated by dividing the cost by the number of TARPs.

Cost per thousand (CPM) is a marketing metric used to indicate the cost per thousand impressions. It is calculated by dividing the total costs by the number of impressions divided by 1000.

Cost per view (CPV) is a marketing metric often used in video advertising to indicate the cost per view, noting that different platforms use differing definitions for what a view is. It is calculated by dividing the total cost by the number of views.

Cost per viewable impression or vCPM, represents the cost per thousand viewable impressions. It differs from CPM as it takes into account how many people actually see ads.

Return on ad spend (ROAS) measures the business revenue earned for each dollar spent on advertising. It is commanly used to assess the effectivness of performance advertising.

When working in paid search there is often a need to calculate the total available impressions for a given keyword. The number of available impressions is calculated by dividing the number of impressions you have purchased for a given advertiser by the impression share. It is important to note that this is not an exact metric due to the way impression share is calculated.