What is CPM?
CPM stands for cost per mille — “mille” is Latin for thousand. It is the price an advertiser pays for 1,000 impressions (views) of an ad, and the standard way to compare the cost of display, video and social media campaigns.
| To find | Formula |
|---|---|
| CPM | Cost ÷ Impressions × 1,000 |
| Cost | CPM × Impressions ÷ 1,000 |
| Impressions | Cost ÷ CPM × 1,000 |
CPM vs CPC vs RPM
- CPM — the advertiser pays per 1,000 impressions, whether or not anyone clicks.
- CPC — cost per click: total cost ÷ clicks. Better when the goal is traffic.
- RPM — revenue per mille: what a publisher earns per 1,000 page views (earnings ÷ page views × 1,000). Same formula, seen from the publisher's side.
Worked example
You spend $1,200 on a campaign that gets 400,000 impressions and 2,000 clicks. CPM = 1,200 ÷ 400,000 × 1,000 = $3.00. CTR = 2,000 ÷ 400,000 = 0.5%. CPC = 1,200 ÷ 2,000 = $0.60.
CPM varies widely by platform, country, audience and season, so compare your own campaigns over time rather than relying on industry averages. For other business maths, see the percentage calculator and the invoice generator.
CPM, CPC and CPA: which one to optimise?
| Metric | Formula | Best for |
|---|---|---|
| CPM | Cost ÷ impressions × 1,000 | Brand awareness, reach |
| CPC | Cost ÷ clicks | Driving traffic |
| CPA | Cost ÷ conversions | Sales, sign-ups, leads |
| CTR | Clicks ÷ impressions × 100 | Ad relevance |
The metrics are linked: CPC = CPM ÷ (CTR × 10) when CTR is in percent. A $4 CPM with a 0.8% CTR gives a CPC of 4 ÷ 8 = $0.50. Improving your CTR lowers your cost per click even if the CPM stays the same.
RPM for publishers
Website owners and creators use RPM (revenue per mille) with the same formula: earnings ÷ page views × 1,000. A site earning $180 from 60,000 page views has an RPM of $3.00. Comparing RPM across pages shows which content earns the most per visitor.
Why CPM changes
CPM rises with competition for the same audience: it is usually higher for wealthy countries, narrow targeting, and the end-of-year shopping season, and lower for broad audiences and quieter months. Track it alongside the result you actually want, such as cost per sale.
To compare campaign results from one month to the next, use the percentage increase calculator; to bill a client for a campaign, the invoice generator creates a PDF invoice.