CPM (Cost Per Thousand Impressions) is a digital marketing metric that measures the cost of 1,000 impressions (views) of an ad. It helps advertisers understand the cost-effectiveness of their ad campaigns in terms of visibility.

Formula:
CPM = (Total Cost of Ad Campaign / Total Impressions) × 1000

Explanation:
Total Cost of Ad Campaign: The amount spent on the ad.
Total Impressions: The total number of times the ad is displayed.
For example, if you spent $500 on an ad that generated 200,000 impressions, the CPM would be:
CPM = (500 / 200,000) × 1000 = 2.5

So, the cost per 1,000 impressions is $2.50.