Glossary
What is CPM in advertising?
CPM is the average price of 1,000 ad impressions. It tells you what attention costs, not whether the attention paid off. Meta’s Ads Insights API reports it as “the average cost for 1,000 impressions”.
Updated 6 October 2026
Cost per mille: the average amount you pay for 1,000 impressions of an ad. Work it out as total spend divided by impressions, multiplied by 1,000.
How CPM is worked out
The formula is spend ÷ impressions × 1,000. The “M” is the Roman numeral for a thousand, which is why the metric is sometimes written as cost per mille. Meta’s insights reference defines an impression as the number of times your ads were on screen, and CPM as the average cost for 1,000 of them.
Take a Reel ad that cost $50 and was on screen 20,000 times. Divide 50 by 20,000 and you get $0.0025 an impression. Multiply by 1,000 and the CPM is $2.50. The same maths works backwards: at a $2.50 CPM, a $100 budget buys about 40,000 impressions.
Meta also labels the spend figure itself as an estimate, so CPM in a report is only as exact as that number.
What CPM does not tell you
Impressions are not people. Meta’s reference notes that reach is different from impressions, because impressions may include several views by the same account. If one person sees your ad four times, CPM counts four impressions. A separate Meta field, cost per 1,000 accounts reached, covers the other view, and Meta marks it as estimated.
A low CPM can also be a bad sign. Cheap impressions in front of people who never click are still wasted money. A $2 CPM that produces no sales loses to a $15 CPM that produces many.
Tip: Compare CPMs only between ads with the same objective and format over the same dates. A comparison of a Story ad against a carousel, or a launch week against a quiet one, tells you very little.
Where CPM fits in the chain
CPM sits at the start of a chain. Impressions become clicks (the click-through rate), clicks become results (the conversion rate), and every step multiplies the cost. If CPM is $3 and 1 in 100 impressions gets a click, ten clicks come from each $3 spent. The cost per click is then $0.30.
Use CPM as a diagnostic. When costs jump, it helps to know whether you are paying more to be seen (CPM up) or being seen and ignored (CTR down).
An example
A bakery spends $80 on a Reel ad that is on screen 32,000 times. Its CPM is $2.50. A week later the same ad costs $80 for 20,000 impressions, a CPM of $4. The bakery checks whether the audience or the dates changed.
Questions people ask
What does CPM stand for?
Cost per mille, meaning cost per thousand. The M comes from the Latin for a thousand. In Meta’s Ads Insights reference it is the average cost for 1,000 impressions of your ad.
How do I calculate CPM?
Divide your total spend by the number of impressions, then multiply by 1,000. For example, $60 spent over 24,000 impressions is 60 ÷ 24,000 × 1,000, which gives a CPM of $2.50.
Is a low CPM good?
Not by itself. A low CPM only means impressions were cheap. If those impressions bring no clicks or sales, the ad is still poor value. Judge CPM together with click-through rate, cost per result and return on ad spend.
What is the difference between CPM and reach?
CPM is priced on impressions, which count every time your ad was on screen, including repeat views by the same person. Reach counts each account once. Meta’s reference says reach differs from impressions for this reason.
Does CPM apply to organic posts?
No. CPM is an advertising price. An organic post has no spend, so there is nothing to divide. You can see how often an organic post was shown, but not a cost per thousand.
Sources
Related terms
- ImpressionsImpressions are the number of times content or an ad was shown on a screen, counting repeat showings to the same person. Reach counts the people instead.
- ReachReach is the number of unique accounts that saw a post, Reel or Story at least once. An account that sees it again doesn’t add to it.
- CPCCost per click: the average you pay each time someone clicks your ad. Work it out as total ad spend divided by the number of clicks.
- Click-through rate (CTR)The percentage of people who clicked or tapped after seeing an ad, link or button: clicks divided by the number who saw it, times 100.
- Conversion rateThe percentage of people who finished a chosen goal, such as buying or signing up, out of everyone who could have: conversions divided by visitors, times 100.
- ROASReturn on ad spend: revenue attributed to your ads divided by what you spent on them. A ROAS of 3 means three units of sales for every one unit of ad spend.
More terms
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