Cost per thousand impressions in one step — and, from the same numbers, the two figures that tell you whether those impressions were worth buying: CPC and CTR.
Enter ad spend and impressions above — your CPM appears here instantly.
CPM — cost per mille, mille being Latin for thousand — answers one narrow question: what did it cost to put your ad in front of a thousand pairs of eyes? It is the standard pricing unit for display, video and social awareness campaigns because it lets you compare the price of attention across platforms that report very different raw numbers. A campaign that spent $500 for 100,000 impressions and one that spent $50 for 10,000 impressions cost exactly the same per unit of attention — a $5 CPM — even though one budget is ten times the other. What CPM deliberately does not tell you is whether anyone noticed, clicked or bought. It is a price metric, not a performance metric, and treating a cheap CPM as a good result is the awareness-campaign version of judging a shop by how many people walked past its window.
CPM = (Ad spend ÷ Impressions) × 1,000. The multiplication by a thousand is pure convention — it rescales a tiny fraction of a cent per impression into a number humans can compare at a glance. Two related figures fall out of the same inputs, and this page shows both when you add clicks: CPC (cost per click) = Ad spend ÷ Clicks, and CTR (click-through rate) = Clicks ÷ Impressions × 100. The three are linked: a high CPM with a strong CTR can produce a cheaper CPC than a bargain CPM that nobody clicks, which is why CPM should never be read alone.
1. Take spend and impressions from the same campaign and the same date range — a lifetime spend figure against last week's impressions produces a CPM that means nothing.
2. Enter both numbers, in any currency. Add clicks if the platform reported them.
3. Read CPM as the price of attention, then check CPC and CTR before concluding anything: cheap impressions that never turn into clicks are usually the most expensive traffic you buy.
A campaign spends $500 and delivers 100,000 impressions: CPM is (500 ÷ 100,000) × 1,000 = $5.00. If those impressions produced 2,000 clicks, CTR is 2,000 ÷ 100,000 = 2%, and CPC is 500 ÷ 2,000 = $0.25 per click. Now compare a second campaign at a tempting $2 CPM that earns a 0.2% CTR: its CPC is $1.00 — four times the cost per actual visitor, from the "cheaper" campaign. That inversion is the single most useful thing a CPM calculator can show you.
There is no universal good CPM — there is only a good CPM for your audience and your goal. Broad, untargeted display inventory can clear below $2; narrow B2B or professional audiences on video and social platforms routinely cost $30 or more, and can still be profitable because each impression reaches someone worth reaching. Prices also swing with season (the November–December auction crush is real), geography, and placement quality. The honest comparisons are: your CPM on the same platform over time, your CPM for one audience against another in the same campaign, and — above all — what that CPM becomes once CTR converts it into a cost per click or per customer. A rising CPM with a rising CTR may be a fine trade; a falling CPM with a falling CTR usually means the platform is finding you cheaper, worse inventory.
Comparing across platforms raw: an impression is not a standardised unit — viewability rules and what counts as "served" differ between platforms, so a cross-platform CPM gap may be measurement, not price. Optimising for CPM alone: platforms will happily find you the cheapest eyeballs available, which are cheap for a reason. Ignoring frequency: the same thousand impressions shown ten times to the same hundred people is a very different purchase from a thousand fresh viewers at the same CPM. Mixing currencies or periods: spend in one currency and a blended lifetime impression count quietly corrupts every comparison you build on the result.
Why "per thousand" instead of per impression? Pure convention, inherited from print advertising rate cards. A single impression typically costs a fraction of a cent, which is unreadable; pricing per thousand keeps the numbers in a range people can negotiate over.
Is a lower CPM always better? No. CPM measures the price of impressions, not their value. Judge it alongside CTR, CPC and ultimately cost per conversion — the cheapest attention is frequently the kind that never buys.
How do CPM and CPC campaigns differ? Under CPM buying you pay for delivery and carry the risk that nobody clicks; under CPC buying you pay only for clicks and the platform carries that risk, which is why CPC inventory usually costs more per unit. The formulas above let you convert either model into the other's terms for an honest comparison.
Are my numbers uploaded? No. The calculation runs entirely in your browser — nothing you type here is sent anywhere.