What is CPM (cost per mille)?
Also called CPM, cost per thousand impressions, cost per 1,000 impressions.
CPM stands for cost per mille, mille being Latin for thousand: the amount an advertiser pays for every 1,000 times an ad is shown. It is calculated as amount spent divided by impressions, multiplied by 1,000.
Why it matters
CPM tells you how expensive it is to get your ad seen, regardless of what happens next. It is useful for comparing audiences, placements and times of year, and for awareness campaigns where being seen is the goal. On its own, though, it says nothing about whether anyone clicked, called or bought.
Example
A gym runs two versions of a January ad. The one aimed at a broad area has a lower CPM, but the one aimed at people within two miles brings more trial sign-ups, so the gym keeps the local version despite its higher CPM.
How CPM is calculated
Meta defines CPM as the amount spent on an ad campaign, divided by impressions, multiplied by 1,000. Here is a worked example with made-up numbers, for illustration only:
Say you spend $30 on an ad and it gets 12,000 impressions. CPM = $30 ÷ 12,000 × 1,000 = $2.50. In other words, every 1,000 times your ad appeared on someone's screen cost you $2.50.
To work backwards, multiply: if a platform estimates a $4 CPM and you want 50,000 impressions, the cost would be about 50,000 ÷ 1,000 × $4 = $200. Real costs change constantly with the auction, so treat any estimate as a rough guide.
Impressions are not people
An impression counts each time the ad is shown, so one person who sees your ad three times adds three impressions. That is why CPM can look cheap while relatively few different people saw the ad. Meta also reports a separate cost per 1,000 Meta accounts reached, which is based on reach instead. Comparing the two, along with frequency (the average number of times each person saw the ad), shows how often the same people are seeing it.
What changes your CPM
Because most social ads are sold by auction, CPM goes up and down with demand. Factors include:
- Audience: narrow or much-wanted audiences usually cost more to reach than broad ones.
- Competition: busy shopping periods attract more advertisers bidding for the same people.
- Placement: feed, Stories, Reels and other placements are priced differently.
- Ad quality: ads the platform predicts people will find relevant may cost less to deliver.
- Goal: an ad optimised for sales or leads may show to fewer, pricier people than one optimised for reach.
Common questions
What is a good CPM?
There is no universal good number, because CPM varies by platform, country, audience and season. Compare your own campaigns against each other over time, and judge success by cost per result, not CPM alone.
What's the difference between CPM and CPC?
CPM is the cost per 1,000 impressions, so it measures the price of being seen. CPC is the cost per click, so it measures the price of getting someone to act on the ad.
Do I pay by CPM?
Often, yes. Many social ads are charged per impression, and the platform reports the result as CPM. Depending on your goal and settings, some platforms let you be charged for other actions, such as link clicks, instead.
Why did my CPM suddenly go up?
Usually because more advertisers are competing for the same people, for example before big shopping dates, or because your audience got narrower or your goal changed. An ad people have seen many times can also become less efficient. Check what changed before raising your budget.
Source: Meta Business Help Centre: CPM (cost per 1,000 impressions), checked 14 October 2026