The CPM, the cost or the number of impressions of a campaign, with every step of the working.
CPM (cost per thousand impressions)
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Enter the two figures you know to see the result.
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CPM, or cost per mille, is the price of a thousand ad impressions, each impression being one showing of an ad. Choose what to work out, enter the two figures you know and get the third, with the working. Add the number of clicks to get the click-through rate (CTR) and the cost per click (CPC) as well. No 'typical' CPM is built in: prices vary by platform, by format and through the year.
'The CPM' starts from the cost and the number of impressions, for example to compare two finished campaigns. 'The cost' starts from a CPM and a number of impressions, to price a media plan. 'The impressions' starts from a budget and a CPM, to see how many impressions the budget pays for.
The cost and the CPM must cover the same campaign, the same period and the same basis: with or without VAT, with or without agency and platform fees. The impressions are the ones your ad server or platform counts; some measures count only the impressions that could actually be seen, which changes the result.
Amounts are rounded to the nearest penny, with a half penny rounded up, and the CTR to two decimal places. A CPM that falls between two pennies is also given to four decimal places. Impressions are rounded down to a whole number, because a budget cannot pay for part of an impression. Copy the working in one click, export it as a CSV file or save it to Priostack.
CPM = cost ÷ impressions × 1,000
Cost = CPM × impressions ÷ 1,000
Impressions = budget ÷ CPM × 1,000
With clicks: CTR = clicks ÷ impressions × 100, and CPC = cost ÷ clicks.
A campaign costs £750 for 300,000 impressions: CPM = £750 ÷ 300,000 × 1,000 = £2.50. It brought 600 clicks, so the click-through rate is 600 ÷ 300,000 × 100 = 0.2% and the cost per click £750 ÷ 600 = £1.25. At the same CPM, a £2,000 budget would pay for £2,000 ÷ £2.50 × 1,000 = 800,000 impressions.
Divide the cost by the number of impressions and multiply by 1,000. A campaign that cost £450 for 180,000 impressions has a CPM of £450 ÷ 180,000 × 1,000 = £2.50. CPM counts showings, not people: if one person sees the ad three times, that is three impressions.
Divide the budget by the CPM and multiply by 1,000. £1,500 at a CPM of £6 buys £1,500 ÷ £6 × 1,000 = 250,000 impressions. When the division is not exact, the calculator rounds down to a whole impression.
They are three ways of paying for online ads. Under CPM the advertiser pays each time the ad is shown, whatever the viewer then does; under CPC, only when someone clicks; under CPA, only when someone takes an agreed action, such as adding a product to the basket or signing up to a newsletter (CMA, Appendix C, paragraph 209). CPM and CPC are linked: CPC = CPM ÷ (10 × CTR in %). At a £5 CPM and a 0.5% CTR, each click costs £5 ÷ 5 = £1.
Yes, with revenue in place of cost: ad revenue ÷ impressions × 1,000 gives what a thousand impressions earned. This is how the Competition and Markets Authority worked out the average CPM of the large platforms in its 2020 market study of online advertising (Appendix C, paragraph 211). Enter the revenue in the 'Cost or budget' field.
Usually the two do not count the same things. Some measures count only viewable impressions, leaving out, for example, an ad nobody scrolled down to (CMA glossary, 'Viewability'). The cost may or may not include intermediaries' fees: the CMA's estimate of a £2 average CPM included the fees of demand-side platforms but not those of media agencies, data providers or ad verification services (Appendix C, paragraph 239). Check too that the cost and the impressions cover exactly the same period.
The calculation is the same either way. What matters is comparing CPMs worked out on the same basis: if your rate card is before VAT, enter the cost before VAT.
This calculator gives general information, not legal, tax, financial or accounting advice. Real CPMs depend on your contracts and platforms: check them against your delivery reports and invoices.
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