How to calculate CPM
To calculate CPM, divide the amount spent by the number of impressions and multiply by 1,000. Meta defines its CPM column exactly this way, as amount spent divided by impressions, multiplied by 1,000,[2] and Google Ads uses CPM for bidding where you pay per thousand impressions.[1]
- CPM$5.00
- Cost per impression$0.0050
- CTR0.8%
- Effective CPC$0.63
Calculating cost per impression is the same division without the × 1,000: $750 ÷ 150,000 = $0.005. Prices that small are hard to compare, which is why buyers quote per mille (per thousand). With clicks entered, the calculator also shows the clickthrough rate and what each click really cost; the CPC calculator turns any CPM and CTR into an effective cost per click.
Impressions a budget buys at each CPM
The number of impressions a budget buys is budget ÷ CPM × 1,000, so halving the CPM doubles the impressions.
| CPM | $100 | $500 | $1,000 | $5,000 |
|---|---|---|---|---|
| $2.00 | 50,000 | 250,000 | 500,000 | 2,500,000 |
| $5.00 | 20,000 | 100,000 | 200,000 | 1,000,000 |
| $10.00 | 10,000 | 50,000 | 100,000 | 500,000 |
| $20.00 | 5,000 | 25,000 | 50,000 | 250,000 |
| $35.00 | 2,857 | 14,285 | 28,571 | 142,857 |
To turn impressions into people reached and frequency, use the impression calculator. For what CPM means on different platforms (vCPM, eCPM, RPM), see the CPM definition.
What counts as an impression
An impression is one time an ad is shown. Meta counts the number of times ads were on screen;[3] a viewable impression under the IAB/MRC guideline needs at least 50% of the ad’s pixels in view for one second for display, or two seconds for video.[4] Paying on a viewable basis (vCPM) usually means a higher price per thousand but fewer wasted impressions, so compare CPMs only when the impression definition matches.
Mistakes that distort CPM
- Comparing CPM with RPM. YouTube defines CPM as the cost per 1,000 ad impressions before its revenue share, and RPM as a creator’s revenue per 1,000 views after the share.[5] They are different numbers on different sides of the auction.
- Dividing by thousands twice. If a report already shows impressions in thousands (“150K”), enter 150,000, not 150.
- Judging a campaign on CPM alone. A cheap CPM with almost no clicks can cost more per result than an expensive one. Check cost per result with the CPA calculator.
- Mixing currencies or tax. Some accounts report spend including VAT or in a different currency from the invoice; keep cost and impressions from the same report.
Not affiliated with Google, Meta, YouTube or the IAB. Platform names are trademarks of their owners and appear only to identify whose documentation we cite.
Frequently asked questions
How do you calculate CPM?
CPM = cost ÷ impressions × 1,000. $750 ÷ 150,000 × 1,000 = $5.00.
How do I calculate cost per impression?
Divide cost by impressions: $750 ÷ 150,000 = $0.005 per impression. Multiply by 1,000 to get CPM.
How many impressions does $100 buy?
$100 ÷ CPM × 1,000. At a $5 CPM that is 20,000 impressions; at $20 it is 5,000.
What does the M in CPM stand for?
Mille, Latin for thousand: CPM is cost per mille, the cost of 1,000 impressions. The CPM definition page explains the variants.