CPM Calculator: Cost per 1,000 Impressions

The CPM formula

CPM stands for cost per mille, mille being Latin for thousand. It is the price of 1,000 ad impressions: CPM = total cost ÷ impressions × 1,000. Rearranged, total cost = impressions × CPM ÷ 1,000, and impressions = cost ÷ CPM × 1,000. The calculator solves for whichever one you choose.

Why per thousand? A single impression costs fractions of a cent, which is awkward to quote. A $5 CPM means each impression costs half a cent, $0.005. Scaling to a thousand makes prices readable and easy to compare across campaigns and platforms.

Worked examples

Buying: a campaign spends $500 and delivers 100,000 impressions. CPM = 500 ÷ 100,000 × 1,000 = $5.00. Planning: you have a $3,000 budget and a platform quotes a $12 CPM. Impressions = 3,000 ÷ 12 × 1,000 = 250,000. Forecasting cost: you need 2 million impressions for a product launch at an $8 CPM. Cost = 2,000,000 × 8 ÷ 1,000 = $16,000.

Publishing: the same math gives RPM, revenue per 1,000 pageviews. A blog that earned $600 from 50,000 pageviews has an RPM of $12. Put revenue in the cost field and pageviews in the impressions field. RPM is the number publishers and AdSense reports use to compare pages, because it captures ad rate and ad density together.

CPM versus CPC, CPA, and eCPM

CPM pays for exposure. CPC (cost per click) pays only when someone clicks, and CPA (cost per acquisition) only when they convert. To compare a CPM buy against a CPC buy, convert: effective CPC = CPM ÷ (1,000 × CTR). A $10 CPM with a 1 percent click-through rate costs $1.00 per click; at 0.5 percent CTR, it is $2.00 per click.

eCPM, or effective CPM, expresses any pricing model as a CPM so you can compare them. If a CPC campaign cost $400 for 80,000 impressions, its eCPM is $5. Choose CPM when the goal is awareness and reach; choose CPC or CPA when you care about actions and have tracking in place.

What drives CPM up or down

Targeting is the biggest factor. Broad audiences on open programmatic exchanges are cheap; narrow audiences such as B2B decision-makers, high-income households, or specific US metros cost far more. Format matters too: video and connected TV typically cost more than static display, and premium placements like homepage takeovers are priced highest.

Seasonality is predictable. CPMs climb through Q4 as retailers compete for holiday shoppers, peaking around Black Friday and Cyber Monday, then drop sharply in January when budgets reset. If your product isn't seasonal, January and February can deliver the same impressions for noticeably less. Geography matters as well: US, UK, Canadian, and Australian audiences command higher CPMs than most other markets.

Mistakes to avoid

Judging a campaign on CPM alone. A $2 CPM that reaches bots or people outside your market is more expensive than a $15 CPM that reaches buyers. Check viewability: the industry standard from the IAB and Media Rating Council counts a display ad as viewable when 50 percent of its pixels are on screen for at least one second, or two seconds for video. Many cheap impressions are never actually seen.

Mixing up impressions and reach. One person can see an ad five times, which is five impressions but a reach of one. Frequency, impressions divided by reach, tells you how often the same people saw it. Also keep platform fees in mind: if an agency or platform takes a cut, your working CPM is higher than the quoted one.

Using the calculator

Pick what to solve for, then fill in the other two values. The results also show cost per single impression, how many impressions a dollar buys, and the cost of one million impressions, a figure media planners often quote. Nothing you enter is uploaded.