CPM Calculator
CPM is cost per thousand impressions: spend ÷ impressions × 1,000. Spend $1,200 to serve 100,000 impressions and your CPM is $12. Rearranged, a $12 CPM buys about 83,333 impressions per $1,000. The M means thousand, not million — it prices attention, not results.
Enter any two, get the third
The box you pick becomes the answer. Fill in the other two.
What the media actually cost over the period.
Times the ad was served, not people reached.
Calculated for you. Change “solve for” to enter it yourself.
$1,200.00 buys 100,000 impressions at this rate.
How to use this calculator
Pick which number you are missing in the “solve for” box, then fill in the other two. The box you are solving for locks and fills itself in as you type. Use it to price a media plan before you buy — solve for spend when a publisher quotes you a CPM and an impression volume — or to check what you actually paid after the fact by solving for CPM.
One thing to keep straight: impressions are how many times an ad was served, not how many people saw it. A campaign reaching 20,000 people five times each records 100,000 impressions. If reach is what you care about, take the reach figure from the platform rather than dividing impressions by a guess.
A worked example
A contractor spends $1,200 on a local awareness campaign and the platform reports 100,000 impressions. CPM is 1,200 ÷ 100,000 × 1,000 = $12. That is $0.012 per impression, or about 83,333 impressions per $1,000.
Now price the next quarter. To hit 500,000 impressions at the same $12 CPM, budget 12 × 500,000 ÷ 1,000 = $6,000. Assume the rate holds and you will be wrong — CPMs drift up as you exhaust the cheapest inventory and jump hard in November and December. Build in headroom or expect to buy fewer impressions than the plan says.
What a good and a bad result look like
There is no good CPM in isolation, because CPM prices access to an audience rather than results from it. Broad awareness placements typically run cheap, tightly targeted professional or high-value consumer audiences run expensive, and premium video runs more expensive still. Those are loose ranges, not benchmarks, and a campaign at three times the CPM can be the cheaper campaign once you count what it produced.
The bad result to watch for is a CPM that falls month over month while enquiries stay flat or drop. That is almost always the audience getting broader rather than the buying getting smarter. The other one is a CPM climbing steadily on a campaign that has not changed, which usually means the creative has fatigued and the auction is charging you for the audience's indifference.
The mistake almost everyone makes
- Reading the M as million. It is the Roman numeral for a thousand. A $12 CPM is $12 per thousand impressions, not per million, and getting this backwards is off by a factor of a thousand.
- Treating impressions as people. Frequency inflates impressions. The same person seen six times is six impressions and one potential customer.
- Optimising for the cheapest CPM. Broadening the audience always lowers it, and usually lowers results at the same time.
- Comparing across platforms as if they measured the same thing. A viewable video impression and a below-the-fold display impression both count as one, and are not remotely equivalent.
- Forgetting fees. Platform CPM is media only. Add agency and production cost before comparing a self-run campaign against a quoted media plan.
Where to look next
CPM prices the top of the funnel and nothing else. Follow the same spend down: the conversion rate calculator shows what share of the resulting traffic does something, the cost per lead calculator prices each enquiry, and the ROAS calculator tells you whether any of it paid for itself.
Common questions
How do you calculate CPM?
Divide total spend by impressions, then multiply by 1,000. Twelve hundred dollars spent to serve 100,000 impressions is 1,200 ÷ 100,000 × 1,000 = a $12 CPM. The M is the Roman numeral for a thousand, not "million" — CPM has always meant cost per thousand impressions, which trips up almost everyone the first time.
How do you work out impressions from a budget and a CPM?
Multiply the budget by 1,000 and divide by the CPM. A $5,000 budget at a $12 CPM buys 5,000 × 1,000 ÷ 12 = roughly 416,667 impressions. Run it the other way to price a campaign: spend equals CPM times impressions divided by 1,000, so 250,000 impressions at a $12 CPM costs $3,000.
What is a good CPM?
Cheap and good are not the same thing here. CPM varies enormously by platform, audience, format and season — broad awareness placements often run in the low single digits while tightly targeted professional audiences or high-demand video inventory can cost many times that. A low CPM reached by advertising to people who will never buy is the most expensive kind of cheap. Judge CPM only after checking what it produced downstream.
What is the difference between CPM and CPC?
CPM prices a thousand impressions; CPC prices a single click. With CPM you pay for the ad being shown whether or not anyone reacts, so the risk of a weak creative sits with you. With CPC you pay only on a click, so the platform carries that risk and prices it in. The two connect through click-through rate: CPC equals CPM divided by a thousand times the click-through rate expressed as a decimal.
Why did my CPM go up without me changing anything?
CPM is set by auction demand, not by your account. It rises when more advertisers bid for the same audience, which happens predictably around Black Friday, Christmas and election periods, and it rises when your audience is narrow enough that few people qualify. Creative fatigue does it too: as engagement drops, platforms effectively charge more to keep showing an ad people have stopped reacting to.
Should you optimise for a lower CPM?
Only if the audience stays the same. CPM falls easily by broadening targeting, accepting worse placements or moving to cheaper inventory, and all three tend to reduce results while making the report look better. The metric worth optimising is cost per outcome — lead, booking or sale. A campaign at double the CPM that converts three times better is the one to keep.
Is CPM the same as CPT?
Yes. Cost per thousand and cost per mille are the same measure under different names, and some media buyers use CPT to avoid the confusion caused by people reading the M as million. If a media plan quotes CPT, treat the number as directly comparable to any CPM figure you already have.
Does CPM include ad platform fees?
Whatever is in the spend figure you enter. Platform-reported CPM uses media cost only, so agency fees, creative production and ad-serving costs sit outside it. If you want to know what reach really costs your business, calculate it a second time with the all-in figure — the gap between the two is worth knowing before comparing a self-managed campaign against a quoted media plan.
Keep going
Impressions are the top of the funnel. This is the share of traffic that actually does something.
Free tool Cost Per Lead CalculatorTurn that same spend into the number that matters — what each enquiry cost you.
Free tool ROAS CalculatorRevenue divided by ad spend, plus the ratio your margin actually requires.
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