What is a gross rating point (GRP)?

Gross rating point (GRP) is a common metric in traditional ad buying that measures the impact of a given ad campaign. GRPs quantify impressions as a percentage of a target audience, multiplied by the frequency in which that audience sees the ad. It is most commonly used in traditional ad formats where precise measurement is not possible.

Ratings points are mainly used in media planning and media buying. Since its development in the 1950s, GRPs have been the primary metric for TV advertising buys, with advertisers typically paying publishers based on the ratings points they receive for a particular ad.

While GRP is typically used most in traditional media campaigns, it’s also important for digital and mobile marketers in order to compare and coordinate linear TV and digital advertising campaigns.

GRP is calculated as the percentage of a target demographic that is reached by an ad (known as reach), multiplied by the number of times they’ve seen the ad in a given campaign (known as frequency).

GRP = Reach (% of population reached) × Average frequency (number of ad impressions)

Let’s take an example of a campaign that has an average of 4 impressions by 1,000,000 viewers, out of a total addressable population of 50,000,000 people. In this case:

GRP = (1,000,000 / 50,000,000) x 4

(.02, representing 2% of the population reached) x 4 (frequency)

GRP = 8

The base population is typically the largest measured population with reasonable access to the media source. To get an idea of the total population of a given audience, advertisers look at estimates of past performance of a chosen channel from market research and measurement groups (for linear TV, most commonly Nielsen).

TRP and GRP measure the same thing, but with different levels of specificity. While GRPs show how much of the total population your campaign can reach, TRPs look at the campaign’s performance for a specified target audience within the total population. While GRPs equal one percent of the total audience exposed to an ad, TRPs equal one percent of a given target demographic’s exposure.

When determining the GRPs you want out to achieve in a given media schedule, look at how much of your market you want to reach, and how many times you need to reach your audience to get them to act. GRPs are calculated slightly differently based on the medium, and GRP goals vary across verticals. In general, you should attempt to reach between 50-90% of your target market, and assume it will take at least three exposures for a viewer to act on an offer. New products require more frequency than established products, and complex products or products with a lot of competition will require more frequency.

While GRP has mostly been a metric for linear TV, it also serves as a bridge between traditional and digital media for ad buyers. Some advertisers adopt GRP as a way to compare campaign performance across media formats. Apps such as Facebook and YouTube have partnered with Nielsen’s Digital Ad Ratings in order to compare their ad performance versus traditional TV ads using GRPs, giving large advertisers more complete campaign performance measurement capabilities.