Outdoor advertising is measured differently from online ads. There are no clicks and no cookies, but there are traffic figures, and with them you can calculate quite precisely how many times your campaign is seen.

Here are the terms you need and a worked example.

Four terms

An impression is one opportunity for one person to see the ad. The figure is gross: the same person passing five times counts as five impressions. It is also called OTS, opportunity to see.

Reach is the number of different people who see the campaign at least once.

Frequency is how many times the same person sees it on average. Reach times frequency gives the impressions.

Share of voice is used on digital screens, where several advertisers share the plays. At 12%, your ad shows for 12% of the screen's running time.

All four are explained briefly in the OOH glossary.

The basic calculation

For a banner the calculation is simple:

Impressions = passers-by per day × 7 × number of weeks

A banner is up around the clock and not shared with anyone, so everyone who passes has the opportunity to see it.

An example from Copenhagen

Take two of our scaffolding sites:

Together that is 180,000 a day and 1.26 million a week. Over a six-week campaign that gives around 7.56 million impressions.

Add our digital screen at Gothersgade and Grønnegade at a 12% share, and you get around 33,600 more plays a week.

You can run the calculation yourself with other sites and periods in the campaign calculator.

Things to remember

Impressions are not people. On a route people take every day, many see the same banner again and again. That is a strength, because repetition builds recognition, but it means reach is lower than the impression figure.

Traffic is not attention. Not everyone who passes looks up. A large format, a good site and a simple message raise the share who actually see it.

Compare like with like. Use impressions to compare sites and plans with each other. To compare with other media, work out the price per 1,000 impressions, CPM, the same way for both.

How to measure afterwards

Traffic figures tell you how many people could see the campaign. Whether it worked, you measure in other ways:

  • Awareness before and after, for example with a short survey
  • Searches for your brand during the campaign
  • Visits to shops or a campaign page near the sites

Read more in how to measure your OOH campaign's success, and see what the research says about outdoor in the media mix.