The definition
CPM stands for cost per mille. "Mille" is Latin for thousand, so CPM is simply the cost of one thousand views or impressions. It is one of the most common ways to talk about the price of reach, because it turns any campaign — large or small — into a single comparable number.
The formula:
CPM = (total spend ÷ total views) × 1,000
A worked example
The numbers below are illustrative only — they are arithmetic to show the mechanics, not a statement about any real rates or typical results.
| Illustrative spend | Illustrative views | CPM (spend ÷ views × 1,000) |
|---|---|---|
| $100 | 50,000 | $2.00 |
| $100 | 100,000 | $1.00 |
| $250 | 100,000 | $2.50 |
Read the first row the other way to see the logic clearly: if a rate were $2 per 1,000 views, then 50,000 views would cost $100. That is nothing more than multiplication — a way to understand the unit, not a claim about what anything actually costs on this or any platform.
Why CPM is useful
CPM lets you compare things that are otherwise hard to line up. A campaign that reached 2 million people and one that reached 40,000 are not comparable on raw spend, but their CPMs are directly comparable. It answers a clean question: what am I paying for a thousand pairs of eyes?
It is also the language most media buyers already speak, so it travels well across channels — paid social, display, influencer, and clip programs alike.
What CPM does not tell you
- Quality of the view. A thousand bot views and a thousand engaged viewers can show the same CPM and be worth wildly different amounts.
- What happened after the view. CPM measures reach, not action. For outcomes, pair it with downstream metrics.
- Whether the view was even seen. An impression is a chance to be seen, not proof of attention.
CPM is a cousin of CPV, cost per view, and both feed into how brands estimate earned media value. Use CPM to compare the price of reach — then layer other metrics on top to judge whether that reach was worth it.