CPM (cost per mille)
CPM, or cost per mille, is what an advertiser pays for one thousand ad impressions. The formula is total spend divided by impressions, times 1,000. It is the base price of attention on a platform, and it moves with competition for the audience, the placement, the season and how the platform rates your ad.
Updated
Formula and example
CPM = (spend ÷ impressions) × 1,000.
Example: $600 spent for 150,000 impressions is a CPM of $4.00.
What drives CPM
- Audience competition: narrow, valuable audiences cost more to reach.
- Placement: some surfaces are priced higher than others.
- Seasonality: demand rises around major retail events, and so do prices.
- Ad quality signals: auction platforms generally favour ads people engage with, which can lower the effective price.
How creative connects to CPM
Ad auctions on the major social platforms weigh more than the bid. Ads that people watch, click or engage with tend to be treated as more relevant, so a stronger creative can win impressions at a lower price than a weaker one bidding the same. This is one reason creative testing is often a bigger lever than bid tweaking.
CPM in context
A cheap CPM is not a goal on its own. Inexpensive impressions on an audience that never buys are worse than expensive ones that do. Use CPM to understand cost of reach, and CPA or ROAS to judge whether that reach was worth it.
How the platforms define it
Google Ads describes CPM as bidding where you pay per thousand impressions on the Google Display Network. Existing CPM bids there have been switched to viewable CPM (vCPM), which charges only when the ad can be seen.
So a Display CPM and a CPM reported by a social platform may not count the same impressions. Compare CPMs within one platform.
Questions
- What does the M in CPM stand for?
- Mille, Latin for thousand. CPM is the cost of one thousand impressions.
- Is a lower CPM always better?
- No. Cheap impressions on people who never act are worth less than costlier impressions on likely buyers. Judge CPM alongside CPA or ROAS.
Sources
Read on 27 October 2026. Platforms change specs and policies without notice; check the source before you build to a number.