Daily Junction.mobi portalMarketing · August 1, 2023 · Harper Quinn · 5 min
CPM is the cost of showing your ad one thousand times. Here is what cost per mille means, how it is calculated, and when paying for impressions beats paying for clicks.
Not all advertising is paid for the same way. Sometimes you pay for clicks, sometimes for sales, and sometimes simply for being seen. CPM is the pricing model for that last category — the one you reach for when the goal is to put your message in front of as many of the right people as possible. It is the currency of awareness, and understanding it keeps brand budgets honest.
CPM is the cost of showing your advert one thousand times, where the M stands for mille, the Latin word for thousand. Despite the M, CPM has nothing to do with millions. It is the price an advertiser pays per thousand impressions, and an impression is simply one instance of an ad being displayed to someone.
This makes CPM an awareness-based model. You are buying visibility, not action. Whether anyone clicks, engages or buys is a separate question — with CPM, you have paid the moment your ad appears on enough screens. That is the opposite arrangement to cost per click, where you pay only when someone actually clicks.
The calculation is straightforward once you remember the thousand:
CPM = (Total cost / Impressions) x 1,000
Suppose you spend £500 and your ad is shown 200,000 times:
(£500 / 200,000) x 1,000 = £2.50 CPM
You can also rearrange it to plan a budget. If a publisher quotes a £6 CPM and you want 500,000 impressions, the cost is:
(500,000 / 1,000) x £6 = £3,000
That second use is where CPM earns its keep in practice — it lets you forecast the cost of reach before a campaign begins.
Paying for impressions can seem odd to anyone used to results-based marketing. Why pay to be seen if you cannot prove a sale? The answer is that awareness is real, even when it is hard to attribute. People rarely buy the first time they encounter a brand. They need to recognise it, trust it and remember it — and that familiarity is built through repeated exposure long before any click happens.
CPM is the natural fit for the top of the marketing funnel, where the job is to reach a wide, relevant audience and plant a memory. Typical uses include:
A click-based model asks people to act now. An impression-based model accepts that most of marketing is about being remembered later.
It helps to see the three common models side by side, because each charges for a different thing.
| Model | You pay for | Best for | Main risk |
|---|---|---|---|
| CPM | Every 1,000 impressions | Awareness and reach | Paying for unseen or irrelevant views |
| CPC | Each click | Direct response, traffic | Cheap clicks that never convert |
| CPA | Each acquisition | Measurable sales or leads | Higher unit price, harder to scale |
None is universally better. They simply suit different goals. A launch campaign that needs to be noticed leans on CPM; a campaign chasing immediate sign-ups leans on CPC or cost per acquisition.
The danger with CPM is treating a low price as automatic value. An impression only counts for something if a real person, in your target audience, actually has the chance to see it. Three things quietly destroy the value of cheap impressions:
So a £1 CPM on an untargeted, low-viewability placement can be far worse value than a £5 CPM that reaches the right people in a visible position. The headline number tells you the price, not the worth.
Imagine a brand launch with a £6,000 budget run two ways.
| Metric | Placement A | Placement B |
|---|---|---|
| CPM | £3 | £8 |
| Impressions | 2,000,000 | 750,000 |
| Audience match | Broad, untargeted | Tightly targeted |
| Viewable rate | 40% | 80% |
| Effective viewed-and-relevant impressions | low | high |
Placement A buys far more raw impressions for the money. But once you account for who actually saw the ad and whether they were the right audience, Placement B delivers more genuine, useful exposure despite the higher CPM. Reach is only valuable when it lands on the people you want, in a place they can see.
To get real value from impression-based buying:
CPM is the cost of one thousand ad impressions — cost per mille — calculated as total cost divided by impressions, multiplied by a thousand. It is an awareness model: you pay to be seen, not to be clicked, which makes it the right tool for brand building, launches and the top of the funnel. But a low CPM proves nothing on its own. Impressions only matter when they are viewable and reach the right audience, so judge CPM on the quality of the exposure it buys, not just the price. Used deliberately, it turns the slippery idea of being remembered into a budget you can plan and measure.
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