What is CPM in advertising?
CPM, or cost per mille, is the price an advertiser pays for one thousand ad impressions. A $5 CPM means $5 for every 1,000 times the ad is shown, or half a cent per impression. It is the standard pricing unit for display, video, CTV and audio advertising, and lets buyers compare prices across very different media.
"Mille" is Latin for thousand. To calculate: cost = impressions ÷ 1,000 × CPM. Other models include CPC (per click), CPA (per action) and CPV (per view). Publishers compare earnings across models using eCPM.
CPM says nothing about quality: a cheap CPM filled with bot traffic or unviewable ads can be far more expensive per real person reached than a higher CPM on quality inventory. That is why buyers track cost per viewable, human impression.