Glossary
Cost Per Mille (CPM)
What you pay for one thousand ad impressions, where mille is Latin for thousand, used to price visibility rather than clicks.
Cost per mille, or CPM, is what you pay for one thousand ad impressions. Mille is Latin for thousand. An impression just means your ad was shown once, whether or not anyone clicked it. So CPM prices visibility, not action.
Total spend / Impressions x 1000 = CPM
$50 spent / 25,000 impressions x 1000 = $2 CPM
CPM is common on platforms where the goal is reach or awareness, and it is often how the underlying ad auction actually charges you even when you think in terms of clicks. That link matters. If you pay a $10 CPM and one in a hundred people clicks, you paid $10 for one thousand views and got ten clicks, which works out to a $1 cost per click. Your click-through rate is the bridge between the two numbers.
The practical takeaway for anyone buying make-money-online traffic is simple. A low CPM sounds cheap, but cheap impressions shown to the wrong people are worthless. What matters is whether those views turn into clicks, and whether those clicks turn into sales. CPM is the very top of that chain.
To see how impressions, clicks, and sales fit together, read how paid advertising actually makes money.