CPM formula
CPM = 1,000 × Total Cost ÷ Impressions "Mille" is Latin for thousand, so CPM literally means cost per thousand impressions — a campaign that costs $500 for 100,000 impressions has a CPM of 1,000 × $500 ÷ 100,000 = $5, meaning every 1,000 times the ad was shown cost $5.
How to calculate CPM (and the other two directions)
The same formula rearranges depending on which value you're missing. If you know your CPM and impressions but need the total cost:
Total Cost = CPM × Impressions ÷ 1,000 If you know your budget and CPM and want to find out how many impressions you can buy:
Impressions = 1,000 × Total Cost ÷ CPM Pick whichever one you're solving for at the top of the calculator, and it'll use the matching version of the formula automatically.
Comparing campaigns
Add another campaign to compare CPMs side by side — useful for comparing different platforms, placements, or targeting options. When two or more campaigns have different CPMs, the campaign with the lowest CPM is highlighted.
Frequently asked questions
What's a good CPM?
It varies a lot by platform, format, and audience — video and highly-targeted placements typically cost more per thousand impressions than broad display ads. Compare CPM against your own past campaigns and what you're actually getting for it (clicks, conversions) rather than treating a single number as universally good or bad.
Is a lower CPM always better?
Not necessarily. CPM only measures cost per impression — it says nothing about the quality of those impressions. A higher-CPM campaign reaching a more relevant audience can outperform a cheaper one that reaches people unlikely to ever convert.
What's the difference between CPM and CPC?
CPM measures the cost per thousand impressions, while CPC measures the cost per click. CPC (cost per click) charges only when someone actually clicks. CPM tends to suit brand-awareness goals where visibility itself has value; CPC tends to suit campaigns where the click, not the view, is what matters.