CPM (cost per mille) is what you pay for every 1,000 times an ad is shown. Enter your spend and impressions to get it, or use the same box to check CTR and CPC for the same campaign.
CPM calculator
Enter any two related numbers and the matching metric fills in: spend and impressions give CPM, clicks and impressions give CTR, spend and clicks give CPC.
Spend $2,500 to get 180,000 impressions and your CPM is about $13.89. "Mille" is Latin for thousand, which is why the M is a Roman numeral.
To work backwards, rearrange it. Impressions equal spend divided by CPM, times 1,000, so a $5,000 budget at a $12 CPM buys roughly 416,000 impressions. Budget equals CPM times impressions, divided by 1,000.
CPM is a price for attention, not for results. A low CPM only means impressions are cheap. It says nothing about whether those impressions came from people likely to buy, which is why it's most useful next to click-through rate and cost per click.
Once you know two of them, you know the third. That's the quickest way to see whether a rising cost per click comes from a pricier audience or from weaker creative.
| If this moves… | …and this stays put | Then CPC |
|---|---|---|
| CPM goes up | CTR is unchanged | Goes up. You're paying more for the same click rate. |
| CTR goes up | CPM is unchanged | Goes down. More of the audience you paid for is clicking. |
| CPM and CTR both fall | — | Depends which falls faster. Check the CPC directly. |
The identity is CPC = CPM ÷ (1,000 × CTR), with CTR as a fraction. At a $10 CPM and a 1% CTR, CPC comes to $1.00.