How to calculate CPM, worked through
CPM is cost per mille — cost per thousand impressions — and the formula is spend ÷ impressions × 1000. The ×1000 is the whole point: raw cost-per-impression is a number with too many zeros to compare, so the industry quotes it per thousand. A $500 campaign that served 100,000 impressions works out at $500 ÷ 100,000 × 1000 = $5.00 CPM. Rearranged, the same formula tells you what a buy will cost before you place it: impressions ÷ 1000 × CPM, so 250,000 impressions at a $5 CPM is $1,250.
CPM measures reach efficiency, not results
CPM (Cost Per Mille — "mille" is Latin for thousand) is what you pay for every 1,000 times your ad is shown. It is a reach/efficiency metric, not a performance metric — a low CPM tells you impressions are cheap, but says nothing about clicks, conversions, or revenue. Pair it with CPC or ROAS to judge whether cheap reach is actually working.
Why margin-adjusted CPM matters
Switch to Planning mode and enter your profit margin to see the margin-adjusted CPM — the effective cost per thousand impressions once your target margin is accounted for. This is useful when setting internal budget targets rather than just reporting the raw spend-based number.
There is no universal "good" CPM
CPM is driven by auction dynamics that shift constantly — platform, audience targeting, season, format (video vs. display), and competition all move it, often by 5-10x. Treat any generic "typical CPM" figure as a rough starting point at best; comparing your own CPM across your own campaigns and channels is far more useful than comparing to an industry-wide number.
What this calculator does not cover
This models a single campaign at a point in time — it does not track CPM trends over a flight, viewability or fraud-adjusted impressions, or platform fees layered on top of media cost. For per-click or per-conversion efficiency, see the CPC Calculator.