Case 1
- Media cost
- 15000
- Impressions delivered
- 2400000
6.25
Open with these valuesCPM Calculator
6.25$
Result: 6.25 $CPM is cost ÷ impressions × 1,000 — what a thousand ad impressions cost. A $15,000 placement that delivered 2,400,000 impressions has a CPM of $6.25. The same three numbers answer the other two questions: what a budget buys, and what a booked CPM will bill.
Worked examples
Case 2
- Media cost
- 17000
- Impressions delivered
- 400647
42.43
Open with these valuesCase 3
- Media cost
- 20
- Impressions delivered
- 1000
20.00
Open with these valuesHow it's calculated
CPM = cost ÷ impressions × 1,000
- StepEnter what the placement cost — media spend, not agency fees or production.
- StepEnter the impressions it delivered, as your ad server or the publisher reports them.
- StepDivide the cost by the impressions and multiply by a thousand.
- ResultSwitch the field you solve for to run it backwards from a budget or a booked CPM.
What this number means
CPM prices attention by the thousand. The arithmetic is a division and a factor of a thousand, so nothing on this page is hard except the number you put in the denominator — and that is where campaigns actually go wrong. An impression is not a person and not a view. Under the IAB and MRC counting guidelines it is a response from an ad delivery system, filtered for robots and recorded as late in delivery as the technology allows, which is as close as a server log gets to an opportunity to see. Two things follow. A served impression can be counted for an ad that scrolled past below the fold, which is why the viewable variant exists: at least half the pixels in view for one continuous second, two for video, priced as vCPM. And a thousand impressions is not a thousand people, because the same person is counted again on the next page. That is the difference between gross reach and net reach, and it is the reason two placements with the same CPM can be worth very different money. eCPM is a different animal again: it takes revenue that was earned per click or per action and restates it per thousand, so a publisher can compare it against a CPM deal.
A measurement of responses from an ad delivery system to an ad request from the user's browser, which is filtered from robotic activity and is recorded at a point as late as possible in the process of delivery of the creative material to the user's browser.
The counting rule is a published standard
How an impression may be counted is set by the IAB/MRC measurement guidelines, not by the platform reporting it. The worked figures behind this page come from published reference works, quoted in the file.
Served is not viewable
A served impression counts once the ad begins to render, whether or not it ever entered the viewport. Compare vCPM against vCPM and CPM against CPM; mixing them makes the cheaper number look better than it is.
A thousand impressions is not a thousand people
Impressions are gross contacts, so one person who sees the ad four times is four of them. Divide by frequency to get net reach before comparing a CPM with a cost per person.
Compare like for like
CPM only ranks placements when the audience definition and the counting method match. A cheap CPM against an untargeted audience often costs more per useful contact than an expensive one.
Commonly misread
CPM is the cost of one impression.
It is the cost of a thousand. A $6.25 CPM is $0.00625 for a single impression, and dropping the factor of a thousand is the most common slip in this calculation.
A thousand impressions means a thousand people saw it.
Impressions count contacts, not people, and one person contributes several. Net reach needs the average frequency, which the impression count alone does not carry.
Impressions are whatever the dashboard says.
A count only means what its measurement rules say it means. The IAB/MRC guidelines require filtering for robot traffic and counting as late as possible in delivery.
The lower CPM is the better buy.
Only if both numbers count the same thing for the same audience. A served CPM and a viewable CPM are not comparable, and neither is a broad audience against a targeted one.
Reference table
| Metric | You pay for | Formula |
|---|---|---|
| CPM | 1,000 served impressions | cost ÷ impressions × 1,000 |
| vCPM | 1,000 viewable impressions | cost ÷ viewable impressions × 1,000 |
| eCPM | nothing — it restates other pricing | (CPC × CTR) × 1,000 |
| CPC | each click | cost ÷ clicks |
| CPP | one rating point | cost ÷ rating points |
Questions
How do you calculate CPM?
Divide the cost of the placement by the number of impressions it delivered, then multiply by a thousand. A $15,000 campaign on 2,400,000 impressions works out at $6.25 per thousand.
How many impressions does my budget buy?
Divide the budget by the CPM and multiply by a thousand. At a $20 CPM, $20 buys 1,000 impressions and $5,000 buys 250,000 — set this calculator to solve for impressions and it does that step for you.
What counts as an impression?
Under the IAB/MRC guidelines, a response from the ad delivery system to an ad request, filtered for robot activity and recorded as late as possible in delivery. It means the ad was delivered and began to render, not that anyone looked at it.
What is the difference between CPM and vCPM?
CPM prices served impressions; vCPM prices only the ones measured as viewable — at least 50 % of the pixels in the viewport for one continuous second, or two seconds for video. A vCPM is normally higher than the CPM for the same placement.
What is eCPM, and is it the same thing?
No. eCPM takes revenue earned some other way, usually per click, and restates it per thousand impressions so a publisher can compare it with a CPM deal. It is a yardstick, not a price you are charged.
Is a low CPM always better?
Only when both numbers measure the same thing. Impressions counted differently, or delivered to a broader audience, can make a cheaper CPM the more expensive way to reach the people you want.
Sources and last check
Information, not financial advice.