How to use the CPM calculator
- Choose what you want to find: revenue, CPM or impressions.
- Fill in the other two boxes. The box you are solving for turns into the answer and updates as you type.
- Publishers can use the second panel: enter earnings and page views from your ad dashboard to get page RPM.
- Add next month’s expected page views to project earnings at the same RPM.
CPM, RPM and the formulas behind them
CPM stands for cost per mille, Latin for thousand. It is the price of 1,000 ad impressions. Advertisers pay it, and publishers earn a share of it. RPM, revenue per mille, measures what a publisher actually earns per 1,000 page views or impressions after the network’s cut, unfilled ad slots and clicks are all counted.
Worked example
A campaign buys 250,000 impressions at a $4.50 CPM: 250,000 ÷ 1,000 × $4.50 = $1,125.00 of spend. Flip it around and a $500 budget at a $2.50 CPM buys 200,000 impressions.
A blog that earned $1,250 from 400,000 page views has a page RPM of $1,250 ÷ 400,000 × 1,000 = $3.125, shown as $3.13. If traffic grows to 500,000 page views at the same RPM, earnings would be about $1,562.50.
Why page RPM and CPM rarely match
One page view can show several ads, and some ad slots go unfilled. So page RPM roughly equals CPM × ads per page × fill rate, after the network’s revenue share. Networks that pay per click, as AdSense does for many ads, blend click earnings into RPM too. Comparing RPM across months is more useful than chasing a single CPM figure, because RPM reflects everything that changed on your pages.
The CPC-to-CPM formula helps advertisers compare buying models. A $1.20 cost per click with a 0.5% click-through rate works out to an effective CPM of $6.00.
Key features
- Solves for revenue, CPM or impressions from the other two.
- Page RPM and a simple traffic-based earnings projection.
- Per-impression and per-million figures for quick sanity checks.
- Five currencies, including pounds and euros.
Practical use cases
Publishers can check whether a traffic source is worth it. If visitors from one country bring a page RPM twice as high, a smaller amount of that traffic can match a larger amount from elsewhere. Ad rates in the US, UK, Canada and Australia are typically higher than the global average, and many publishers see rates rise in the fourth quarter as holiday budgets peak.
Advertisers can turn a fixed budget into an impression target before booking a campaign, or compare a direct sponsorship quote with network CPMs.
Common mistakes with CPM maths
The most frequent error is dividing by impressions without multiplying by 1,000, which gives a cost per single impression a thousand times too small. Another is comparing a network’s CPM with your page RPM as if they were the same thing. Finally, check whether a quoted CPM is gross (what the advertiser pays) or net (what you receive after the platform’s share).
Creators negotiating a newsletter or podcast sponsorship can convert a flat fee into CPM to see how it compares with display ads.