What Is CPM Advertising? How the Billing Method Works and Points for Choosing It
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Authors: Shusaku Yosa
When you set out to run web advertising, the first thing you decide is the "billing method." The most representative one is CPM advertising. Hearing that "you are charged just for being displayed," many people are puzzled by the difference from CPC (cost-per-click). In this article, we organize how CPM advertising works as a billing method and its calculation, then explain the differences from CPC and CPA, its benefits and drawbacks, and finally the points for choosing whether CPM advertising fits your own objectives, all from a practical standpoint.
CPM advertising is advertising delivered on a billing method (impression-based billing) in which cost is incurred according to the ad's "number of displays." CPM stands for "Cost Per Mille" and is read "see-pee-em." Mille means 1,000 in Latin, and as the name suggests it expresses how much cost is incurred each time the ad is displayed 1,000 times.
Because the number of times an ad is displayed is called "impressions," CPM is translated as "cost per impression." The key point is that you are billed solely by the number of displays, regardless of whether users clicked. It becomes easier to understand if you regard it as the counterpart to "click-based billing (CPC)," where you are billed by the number of clicks.
CPM is calculated by dividing the cost spent on advertising by the number of displays and multiplying by 1,000. The formula is as follows.
CPM (yen) = ad cost / number of impressions x 1,000
For example, if an ad cost of 100,000 yen produced 500,000 displays, CPM is "100,000 / 500,000 x 1,000 = 200 yen." In other words, it costs 200 yen for each 1,000 displays. Conversely, if the CPM rate is set, you can also estimate the approximate number of displays from your budget.
CPM billing is adopted for ads that aim to increase displays and reach a wide range of users. The representative examples are display ads, social media ads, and video ads. Specifically, CPM billing is commonly used in Meta ads (Facebook and Instagram), LINE ads, TikTok ads, DSP ads, and so on. It is a method well suited to ads that want to spread awareness through visual impact.
Web advertising billing methods include CPC and CPA in addition to CPM. Where the billing occurs differs for each.
The further the billing point advances along "display -> click -> result," the closer the user's behavior gets to the goal. Because CPM is billed at the earliest "display" stage, it is suited to delivering broadly to many people, while CPC suits site traffic and CPA suits acquiring direct results.
As a supplementary note, CPM, CPC, and CPA are not only "billing methods" but are also used as "metrics" for measuring advertising effectiveness. For example, it is common to deliver on CPM billing while calculating how much it ultimately cost per click (CPC) and per result (CPA) to evaluate effectiveness. Keeping in mind that they have two faces, billing method and evaluation metric, helps avoid confusion.
Because CPM advertising determines cost by the number of displays, ad costs do not fluctuate much unless you change the bid or delivery settings. With CPC billing, a sudden surge in clicks due to social media virality can cause the bill to spike, but with CPM there is no such worry. It is suited to cases where you want to keep monthly budgets stable.
Because CPM billing is delivered to maximize the number of displays, it becomes easier to catch the eyes of more users. It demonstrates its strength in campaigns at the stage of first making people aware of your existence, such as new product launches or expanding brand awareness.
Because the cost does not change no matter how many clicks occur, the more persuasive and clickable the ad, the lower the effective cost per click. For example, with a CPM of 200 yen and a 1% click rate, one click is 20 yen, but with a 2% click rate it halves to 10 yen. If you can create good ad creative, CPM tends to be cheaper than CPC.
Because CPM is billed simply for being displayed, if there are few clicks or results even when the ad is displayed many times, there is a risk that cost-effectiveness declines. Since you are billed even if the ad is not reaching the intended users, the precision of targeting greatly influences results.
Even if the ad is at the bottom of the page and the user did not scroll that far, it may be counted as one display at the point it was loaded. Caution is needed because cost can be incurred for displays that were not actually seen. As a metric to compensate for this, there is vCPM, described later.
vCPM is a CPM that targets only "displays actually seen by users." On Google and Yahoo!, a state in which 50% or more of the ad area is on screen for one second or longer is judged as "viewable (active view)." It is effective when you want to avoid being billed for unseen displays, and ads that let you select vCPM billing in the settings are increasing.
eCPM is a value that "converts to CPM" an ad delivered on a billing method other than CPM. The formula is the same as CPM: ad cost / number of displays x 1,000. For example, even for an ad delivered on CPC billing, calculating eCPM tells you "how much it cost per 1,000 displays," letting you compare the cost efficiency of ads with different billing methods side by side.
Whether to deliver on CPM or CPC becomes easier to organize when you judge from two perspectives: the "objective of the ad" and "cost efficiency."
First, clarify the objective of the ad. If the goal is "having more people see it," such as expanding awareness of a new product or branding, CPM, which maximizes the number of displays, is suitable. On the other hand, if the goal is "behavior and results," such as site traffic, purchases, or inquiries, CPC and CPA, which bill according to clicks or results, are suitable.
From the perspective of cost efficiency, the click rate (CTR) is a deciding factor. As a general guideline, if the click rate is 0.1% or higher, CPM billing tends to keep costs down, and if it is below 0.1%, CPC billing does. This is because clickable ads are cheaper per click with CPM, while less-clickable ads avoid wasted display billing with CPC.
The initial billing method is no more than an early guideline. Because click rates and results fluctuate once you actually deliver, it is important to review while looking at operational data. For example, adjustments such as "deliver on CPC at first, then switch to CPM once you find the click rate is high" are also effective. Not thinking of it as fixed once decided leads to results.
CPM advertising is advertising on an impression-based billing method in which cost is incurred according to the number of ad displays. Because cost does not change with whether clicks occur, it is easy to keep ad costs stable, and its strength of reaching many users broadly makes it suited to expanding brand awareness. On the other hand, since cost-effectiveness declines when there are few clicks or results, the precision of targeting is the key.
The basic way to choose is to judge on two axes: CPM if the objective is awareness and CPC if it is results, and on the cost side using a click rate of 0.1% as a guideline. First clarify the objective of your ad, deliver small to check the click rate, and adjust to the optimal billing method.
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