Cost per mille (CPM), also called cost per thousand, is a marketing term used to denote the price of 1,000 advertisement impressions on one web page. If a website publisher charges $2.00 CPM, that means an advertiser must pay $2.00 for every 1,000 times their ad is displayed on the publisher’s website. Cost per mille is typically used by online advertisers targeting large groups of internet users.