CPM calculator
CPM stands for cost per mille — cost per thousand — because the Latin numeral stuck when the term came out of print advertising. It survives because impressions are counted in numbers too large to be useful one at a time, and because it makes very different media comparable: a billboard, a podcast read and a display banner can all be quoted per thousand pairs of eyes.
CPM is ad spend divided by impressions, multiplied by a thousand. A 1,000 budget delivering 100,000 impressions is a CPM of 10 — meaning it costs ten to put the ad in front of a thousand people.
How to calculate CPM
CPM measures cost of reach, not value, and that is both its use and its trap. A cheap CPM against a badly targeted audience buys nothing; an expensive CPM against exactly the right thousand people can be the best money in the account. Because CPM is entirely upstream of clicks and conversions, it should be used to compare placements against each other and never to judge whether a campaign worked. That is what the CPA and ROAS rows are for.
Questions
Cost per mille — cost per thousand impressions. The M is the Roman numeral for a thousand.