CPM is the most widely used metric in advertising, and often the most misunderstood. In digital out-of-home — DOOH, for Digital Out-Of-Home — it remains useful for comparing plans, but it does not tell the whole story. Understanding what it actually measures, and what it leaves out, is essential to correctly assess the value of a physical medium.
What CPM is
CPM stands for "cost per mille": the cost of buying one thousand impressions. If a campaign costs $1,000 for 200,000 impressions, its CPM is $5. It is a handy comparison unit, independent of total volume, that allows very different media to be placed side by side. But a CPM only makes sense if you know precisely what an "impression" is for each medium.
Raw CPM versus cost of attention
Raw CPM counts theoretical opportunities to be exposed, without presuming anything about the quality of the contact. The cost of attention — or qualified CPM — instead seeks to relate cost to impressions that are genuinely likely to be seen and noticed. Two campaigns can show the same raw CPM while delivering radically different attention value: it all depends on the context, the duration of exposure and the probability that the message is actually perceived.
The specifics of DOOH
In DOOH, a quality impression rests on several variables specific to the physical venue:
- Presence: how many people are actually within the screen's zone.
- Notice factor: the probability that someone present actually notices the screen.
- Dwell time: the time spent on site, which multiplies the opportunities to see the message.
- Frequency: the number of times the message loops during a single visit.
These dimensions bring DOOH closer to the "opportunity-to-see" logic used in out-of-home standards, far more than to the simple page-load counting of digital.
Why raw CPM understates attention in bars
In a bar, context changes everything. The audience is adult, present for a long time, and in a social state of mind where the eye scans the room. Above all, the screen suffers from none of the avoidance mechanisms of personal digital: zero scroll, zero skip, zero adblock. Where a significant share of digital impressions is never truly seen, attention in a bar can reach around 83% according to our estimates. A raw CPM that ignores this contact quality mechanically underestimates the medium's real value.
Industry standards
OOH and DOOH measurement relies on recognized frameworks: COMMB in Canada, the OAAA for Digital Place-Based standards, the MRC for OOH measurement standards, and Geopath for impressions, reach and frequency in North America. These references provide a common grammar: weighting traffic by visibility and time spent, rather than counting raw exposures.
Limits and honesty
No attention estimate is perfect, and that is precisely why transparency comes first. Our impression volumes are estimated using a methodology inspired by these standards, with conservative assumptions — never presented as certified. To understand how we value attention rather than volume alone, explore our approach to the Qualified CPM, and the detail of our calculations on the methodology page.
Audience figures are estimates based on a methodology inspired by OOH/DOOH standards. See our methodology.