CPM calculator
CPM is the price of being seen a thousand times. It is the number to compare when you are buying attention rather than clicks.
What CPM does and does not tell you
The M is the Roman thousand, not million — the single most common misreading of the term. CPM is spend divided by impressions, times a thousand, and it makes campaigns of different sizes directly comparable.
It measures the cost of reach, not results. A cheap CPM in front of the wrong audience is worse than an expensive one in front of the right one, which is why CPM alone never decides whether a campaign worked. Pair it with click-through rate to see whether the impressions turned into visits, and with cost per acquisition to see whether the visits turned into money.
CPM varies enormously by platform, audience and season. Narrow targeting costs more per impression because you are bidding against everyone else who wants that same specific audience, and the fourth quarter is dramatically more expensive than January because retail budgets flood the auction.
Questions
Is CPM per thousand or per million?
Per thousand — M is the Roman numeral. Cost per million would be a very different and much smaller-looking number.
What is a good CPM?
It depends entirely on platform and audience, and the honest comparison is against your own historical CPM for the same audience. A low CPM in front of people who will never buy is not a win.
Why did my CPM rise without changing anything?
Auction competition. Seasonal demand, especially in the run-up to the holidays, pushes every advertiser's costs up regardless of what they changed.