What an impression multiplier is
An impression multiplier is the average number of people a single play reaches on a given screen. A play is one display of your ad; the multiplier says, on average, how many pairs of eyes that one display is credited with. Multiply the plays a screen ran by its multiplier and you get its estimated impressions. It is the small piece of arithmetic that lets a count of displays be reported as a count of viewers.
The multiplier is not the same on every screen, and that is the point of it. A play on a screen inside a packed rail concourse is seen by far more people than a play on a screen in a quiet office lobby, so the concourse screen carries a much higher multiplier. It is a per-location number, built from audience research for that spot. When you see one impression figure for a whole campaign, it is the sum of each screen's plays multiplied by that screen's own multiplier.
Plays versus impressions
Plays and impressions measure two different things, and the multiplier is the bridge between them. A play is a verified event: the screen showed your ad once, and it is logged. An impression is a modelled estimate of how many people that play reached. Because one play can be credited with many impressions, the impression number is always the larger and always the softer of the two.
This is why the unit you buy on changes what you can trust. Traditional media often quotes a cost per thousand impressions, or CPM, the industry unit that sits directly on top of the multiplier. Change the multiplier and the impression count, and the CPM, moves with it, without a single extra display running. Buying on plays sidesteps that: you pay a set price for a display that is logged as delivered, and the impression estimate rides alongside as context rather than as the meter. The CPM versus per-play guide works through the trade-off in full.
How it is estimated
$0
from, per play, the billed unit
0M+
screens, each with its own multiplier
0+
countries covered
0
verified plays, one worldwide flight
A screen's multiplier comes from audience measurement for its location. The inputs are the familiar ones: pedestrian and vehicle counts passing the site, how long people dwell in view, the size and angle of the screen, and the likelihood a passer-by actually looks at it rather than walking past. Industry bodies such as the World Out of Home Organisation and national audience panels publish the methods; the output for each screen is a figure for average viewers per play. Because every input is a measured or modelled average, the multiplier is an estimate, and so is any impression number built on it.
That is the reason Blindspot keeps the play as the unit you are billed on. The impression estimate is genuinely useful for sizing an audience and comparing places, and the platform reports it, clearly labelled as an estimate, alongside the plays. But your budget is spent against displays that provably ran, priced per play from about $0.23, logged across 3M+ screens in 50+ countries. On one worldwide flight that meant 2,146,892 verified plays, a hard floor of real displays under whatever audience figure sits on top. It is also why the model works as hard on a global flight as on a first campaign: the budget buys the exposure it needs, and the multiplier never inflates what you pay. See how the play is priced in the per-play guide, how it feeds measurement in the measuring a campaign guide, or open the map and build a plan.
The multiplier estimates the audience; the play is what you pay for.
The multiplier, in one line