CostperImpression

Cost per impression is a pricing model used in online advertising in which advertisers pay for each time an ad is displayed to a user. An impression is counted whenever an ad is served to a browser or device, and multiple impressions can be generated by repeat views from the same user. This metric is commonly used for campaigns aimed at broad reach and brand awareness.

The most common related metric is cost per thousand impressions (CPM). CPM is calculated by dividing the total amount spent by the number of impressions, then multiplying by 1,000: CPM = (total spend / impressions) × 1,000. Some vendors report the price on a per-impression basis without the thousand multiplier, in which case cost per impression = total spend / impressions.

Advertisers use cost per impression to compare performance across channels and to estimate reach and budget, particularly for display, video, and social ads. However, a lower CPM does not guarantee favorable outcomes, as impressions may be of low quality or poor targeting. Metrics such as viewability, engagement, click-through rate, and conversions help assess effectiveness. Ad fraud and non-viewable impressions can distort cost-per-impression figures, so many buyers rely on measurement standards and verification services.

Industry standards and measurement: Impressions are defined by organizations such as IAB; viewable impressions require criteria set by MRC and partners, commonly at least 50% of the ad in view for a minimum duration on display and video. Effective cost per mille (eCPM) is another related metric that accounts for revenue per thousand impressions, useful for comparing formats.