How do you calculate CPM?

Divide the ad spend by the impressions and multiply by 1,000. €1,500 for 300,000 impressions is a CPM of €5.00.

What does CPM stand for?

Cost per mille, mille being Latin for thousand: the cost of 1,000 impressions.

What is the difference between impressions and reach?

Impressions count every showing of the ad; reach counts the different people who saw it at least once. 300,000 impressions shown to 120,000 people is a frequency of 2.5, and reaching 1,000 of those people cost 2.5 times the CPM.

No figure fits every store: CPM moves with the platform, the audience, the placement and the season. What matters is what the impressions turn into, so judge a CPM by the CPC and the cost per order it leads to rather than by the CPM alone.

Is a lower CPM always better?

No. A CPM is only as cheap as the clicks and orders it brings: CPC is CPM divided by 1,000 times the CTR. A €10 CPM at a 2% CTR buys clicks at €0.50, half the price of a €5 CPM at a 0.5% CTR.

What is viewable CPM?

A way to buy impressions where you pay only for those that could be seen; Google Ads offers it as vCPM bidding. It counts fewer impressions than a standard CPM, so the two are not directly comparable.

CPM Calculator, Reach and Frequency

Result

Fill in ad spend, impressions to see the result.

How it works

CPM is the cost of 1,000 impressions: the ad spend divided by the impressions, times 1,000. Meta and Google both use it to price reach.

An impression is one showing of an ad, not one person. When the same people see the ad several times, reaching 1,000 different people costs more than the CPM. With your reach, the calculator shows how often the average person saw the ad, and what reaching 1,000 people cost.

CPM = ad spend ÷ impressions × 1,000

frequency = impressions ÷ reach

cost per 1,000 reached =
  ad spend ÷ reach × 1,000

CTR = clicks ÷ impressions
CPC = ad spend ÷ clicks
    = CPM ÷ (1,000 × CTR)

What each term means

Impressions: Every showing of the ad, repeats included, as the platform counts it.
Reach: The different people who saw the ad at least once. Meta counts reach in accounts and reports a cost per 1,000 accounts reached.
Frequency: Impressions per person reached: how many times the average person saw the ad.
CPM: The cost of 1,000 impressions.
Cost per 1,000 reached: The cost of reaching 1,000 different people. It equals the CPM times the frequency.
CTR and CPC: With link clicks: the share of impressions that became a click, and what each click cost.

Each platform counts its own impressions

Each platform decides when an impression counts, and some sell only impressions that could be seen: Google's viewable CPM charges only for viewable impressions. Compare CPMs within one platform, and read a gap between platforms as a difference in what is counted as much as in price.

A cheap CPM is not a cheap result

Cheap impressions are only cheap attention if people act on them. CPC equals CPM divided by 1,000 times the CTR, so a €5 CPM at a 0.5% CTR makes €1.00 clicks, while a €10 CPM at 2% makes €0.50 clicks.

Worked example

Example numbers, round on purpose. They are not a real store.

Ad spend: €1,500
Impressions: 300,000
Reach: 120,000
Link clicks: 2,400

1CPM: €1,500 ÷ 300,000 × 1,000 = €5.00
2Impressions per €1,000 spent: 300,000 ÷ €1,500 × 1,000 = 200,000
3Frequency: 300,000 ÷ 120,000 = 2.5
4Cost per 1,000 reached: €1,500 ÷ 120,000 × 1,000 = €12.50
5CTR: 2,400 ÷ 300,000 = 0.80%
6CPC: €1,500 ÷ 2,400 = €0.625, shown as €0.63

The €5.00 CPM hides a cost of €12.50 to reach 1,000 different people, because the average person saw the ad 2.5 times.

Frequently asked questions

How do you calculate CPM?
Divide the ad spend by the impressions and multiply by 1,000. €1,500 for 300,000 impressions is a CPM of €5.00.
What does CPM stand for?
Cost per mille, mille being Latin for thousand: the cost of 1,000 impressions.
What is the difference between impressions and reach?
Impressions count every showing of the ad; reach counts the different people who saw it at least once. 300,000 impressions shown to 120,000 people is a frequency of 2.5, and reaching 1,000 of those people cost 2.5 times the CPM.
What is a good CPM?
No figure fits every store: CPM moves with the platform, the audience, the placement and the season. What matters is what the impressions turn into, so judge a CPM by the CPC and the cost per order it leads to rather than by the CPM alone.
Is a lower CPM always better?
No. A CPM is only as cheap as the clicks and orders it brings: CPC is CPM divided by 1,000 times the CTR. A €10 CPM at a 2% CTR buys clicks at €0.50, half the price of a €5 CPM at a 0.5% CTR.
What is viewable CPM?
A way to buy impressions where you pay only for those that could be seen; Google Ads offers it as vCPM bidding. It counts fewer impressions than a standard CPM, so the two are not directly comparable.

Related terms: CPM, impression, click-through rate and CPC.

Next: which impressions led to sales?

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