How Do You Calculate OOH Impressions?

While OOH advertising can be more challenging to measure, you can get a good estimate of your audience by employing several different measurement systems. OOH advertising is predominantly measured in four different ways.

How Do You Calculate OOH Impressions?

If you’re used to working with different types of advertising media, it might seem difficult at first to get a sound measurement of how exactly an out-of-home, or OOH, ad campaign is actually performing.

While TV offers you the opportunity to capture ratings on the show that aired your commercial and email marketing tools can tell you exactly how many times your email was opened and how many people clicked the embedded link, OOH advertising doesn’t have such a reliably quantifiable measurement of effectiveness.

So, how do you calculate OOH impressions?

What Is OOH Media?

Out-of-home media, or OOH media, refers to any type of advertising that consumers are exposed to outside of their homes and offline, and it was one of the most common types of advertising for many years.

Out of home advertising types include:

  • Billboards: This traditional form of media is most commonly displayed next to freeways, interstates, highways, and other heavily traveled areas where consumers can see them from passing cars or trains.
  • Street furniture: Street furniture advertisements place ads at eye-level with potential customers. Street furniture advertisements use infrastructure like bus stops, newsstands and kiosks, transit shelters, phone kiosks, and more.
    Commuters, pedestrians, and motorists are the most common targets of street furniture advertising.
  • Wallscapes: Wallscapes are advertisements that use the exterior surfaces of existing buildings to promote brands. These ads may be painted on or be temporary, but they’re often quite beautiful, which makes them part of the urban beautification process. Consumers often view these advertisements as an enhancement rather than as an annoyance, which helps place the product in a positive light.
  • Wildpostings: Cities are synonymous with flyers that promote events, concerts, and special appearances and seem to be plastered to every available surface. These advertisements are called wildpostings, and they’re a popular and low-cost way to get the word out about things like events, album releases, and appearances in urban areas.
  • Transit advertising: Transit advertising includes wraps placed on the sides of busses, trains, subway rail cars, and taxis. Both users of public transportation and commuters within the city, as well as anyone else in the vicinity of these vehicles, are considered targets of the advertisements. Because they’re not stationary, transit advertisements may be able to reach more people than other forms of media.

Nearly any type of OOH advertising can also be converted into digital OOH advertising, or DOOH, creating an advertisement that incorporates new technology while still taking advantage of the many benefits of outdoor advertising.

What Types of OOH Audience Measurement Terms Exist?

Admittedly, measuring OOH advertising audiences is a bit more complicated than measuring in-home advertisements.

After all, ratings tell us how many people watched a television show and saw the commercials, while clicks tell us the number of people who engaged with an email marketing campaign or clicked on a social media promotion.

While OOH advertising can be more challenging to measure, you can get a good estimate of your audience by employing several different measurement systems. OOH advertising is predominantly measured in four different ways.

  1. Impressions: Impressions gauge who your ad is reaching, and are typically provided in the form of weekly figures. Impressions measure the average number of times an individual consumer views an advertisement. Impressions include information about traffic data, which helps estimate the number of vehicles that have passed an advertisement. Impressions may also include travel surveys, data modeling, and census data.
  2. Demographics: Census information and surveys are used to provide demographic and psychographic information that measures OOH advertising. The data is modeled into millions of trip paths, which helps advertisers understand who is being reached by their content.
  3. Digital trails: Digital trails are a simple way to track OOH advertising. They include things like promo codes, social media accounts, links, and other online information that is incorporated into an advertisement. Each of these items can be tracked based on the number of people using a promo code, for example, or following a social media account.
  4. Visibility research: Visibility research is calculated using contact zones that determine the distance from which an advertisement can first be seen and how fast traffic moves past the advertisement each hour. Another calculation is the time in which people “dwell” in an area while sitting in traffic, waiting for a train, or waiting for a bus. Visibility research helps to determine a person’s likelihood of actually noticing an ad based on their opportunity to see it.

How Do You Calculate OOH Impressions?

In the past, OOH impressions have been measured by using traffic counts and daily effective circulation in order to estimate the total number of different consumers within a target audience who are exposed to an advertisement for a product or service, which is called reach.

Daily effective circulation, or DEC, is the measure of traffic that passes by a particular advertisement.

Unfortunately, this information didn’t really tell advertisers how many people were actually seeing their ads, it only measured how many people could be seeing their ads.

Geopath, a non-profit organization formerly known as the Traffic Audit Bureau (TAB), recognized the issue facing advertisers who wanted to know how many people their ads were actually reaching.

They began working to develop a new way to calculate impressions and started conducting experiments in which drivers wore goggles that conducted eye-tracking as they drove.

From this information, they were able to determine what percentage of drivers actually viewed a specific advertisement.

Today, that number is known as the variable adjustment index or VAI. The VAI is used to calculate OOH reach and impressions.

Today, most outdoor advertising companies rely on Geopath for all OOH impressions data and other measurements, as Geopath’s mission is to independently audit and report OOH advertising ratings throughout the United States.

The organization is governed by a three-part board that includes advertisers, agencies, and media companies, so all parties can be assured they are receiving reliable information.

What Are Some Simple Ways to Determine If an OOH Campaign Is Effective?

Sometimes, we get bogged down in producing data, writing reports, and analyzing information to the point that we forget that there are simpler ways to determine if an OOH advertising campaign has been effective.

If you’re simply wondering whether your campaign has caused an increase in business since it began, consider using one of these measurements for your return on investment (ROI).

Slogan Analytics
If you used a particularly catchy slogan or phrase on a recent OOH advertisement, you can use slogan analytics to get an idea of the ad’s effectiveness.

Look on your website’s analytics tool to see how many times the keywords or tagline from your slogan has been entered into search engines.

While people might not be able to remember a promo code or a website, if the slogan stuck with them, they may try to find your brand by searching for the words they remember.

Hashtag Metrics
Hashtags are a great way to measure the success of a billboard or wildposting campaign.

Include a campaign-specific hashtag on your ad and check for its use on different social media platforms.

If you notice people starting to engage with the hashtag, you’ll get an idea of the impressions of your advertisement.

Hashtags also enable you to search across social media platforms to get an idea of the number of people connecting with your brand.

Before and After
If you’re only running one OOH advertising campaign at a time, the before and after method is an obvious way to measure the effectiveness of your campaign.

Take a look at sales immediately prior to starting a campaign, and then look at sales after the campaign begins.

If you notice a significant increase in sales, it’s likely due to your OOH advertising campaign.

The tricky thing about using the before and after method of measurement is that it requires you to keep all other forms of marketing the same.

Otherwise, the variability may be attributable to other campaigns.

Promo Code Campaigns
Adding a promo code to a billboard or flyer helps to measure the impressions of your OOH campaign.

Assign a campaign-specific promo code, discount voucher, or QR code to the campaign, and run the promo code only during the period of the campaign.

This will enable you to track the number of people who enter the campaign-specific code on the website, giving you an idea of how many sales your campaign has generated.

Campaign-Specific URL
Placing a campaign-specific URL on your OOH advertisement is another way to measure impressions.

This URL must only appear on the outdoor ad and should not be used anywhere else.

The URL should link directly to your main website, and traffic from the URL can be used to measure the number of people viewing the ad, making purchases, and spending time on your website, all of which are excellent measures of ROI.

Perhaps the simplest measure of all is to give customers a short survey during or after a purchase that asks them where they heard about your brand.

If they tell you that they first learned about your company on a billboard, then you have your answer about the effectiveness of your OOH campaign!

Contributors Statement

This blog post was a collaboration between the AdQuick team. Chris Gadek, John McClung, and Jack Gaylor contributed to this piece. Payton Biddington created the visuals. If you'd like to learn how out of home can work with your unique marketing campaign and business, send a quick email to [email protected] or call (213) 986-6179. We'll reach out with case studies and recommendations tailored to you.


The opinions expressed are those of the authors. This material has been prepared for educational purposes only. Please be sure to consult with your internal team of stakeholders to assess your specific needs before adapting any practices from this blog, as your own.