Target rating points quantify the exposure level of advertising messages that are delivered to a specific target audience in terms of reach and frequency. TRPs are calculated by multiplying the cumulative reach of the advertising, typically over a one week period, by the frequency of exposure to the advertising. Originally used in broadcast advertising, TRPs are often used to measure advertising impact in online as well as offline media.

GRPs and TRPs

TRPs are a refinement of gross rating points, or GRPs. GRPs relate to the "total audience" exposure to advertising messages, whereas TRPs relate to the "target audience" exposure. In the case of TV, for instance, the A.C. Nielsen Company defines total audience as the percentage of households or individuals watching TV that are tuned into a show that airs your commercial. The target audience, therefore, would be the percentage of the total audience tuned to that show who are most likely to buy your product or service.

Calculating GRPs and TRPs

Each GRP equals 1 percent of the total audience; a TRP equals 1 percent of the target audience. If 40 percent of total TV households saw your commercial one time, that would translate into 40 GRPs. If your target audience was 50 percent of the total audience, that would translate into 20 TRPs.

GRPs and TRPs are cumulative. Assume that your commercial aired five times over a one week period and delivered the following TRPs per airing: 35, 40, 45, 43, and 37. The total delivery would be 200 TRPs. However, 200 TRPs can also be obtained with a 50 percent reach with a 4 frequency, or a 4 percent reach with a 50 frequency. Thus, GRPs and TRPs inform about the quantity of media weights, but not the quality of the weights.

Target Audience

Marketers commonly define target audiences in terms of demographic and psychographic profiles, and with growing frequency, even exographic profiles. Demographics describe "who" your audience is in quantifiable terms such as age, gender, household income and education attainment. Psychographics and exographics attempt to explain the motivational "why's" of consumer behavior.

Media companies, such as A.C. Nielsen, use demographic data to define target audiences for TRP purposes, to the exclusion of psychographic and exographic data. In contrast, marketers must engage in primary research, such as focus groups, or resort to mining data stored in "big data" warehouses to understand motivational issues that drive consumer behavior. Because TRPs ignore the motivation issues of consumer behavior, the metric provides a one-dimensional picture of your target audience, which can result in decisions based on incomplete information.

Use with Caution

Avoid expecting TRPs and GRPs to do more than what they actually do. That your commercial aired on a show does not mean that everyone watching the show actually saw the spot. Some viewers may have been preoccupied with other activities. Moreover, these metrics ignore audience engagement -- the extent to which viewers pay attention to advertising content.

With the growing popularity of online advertising for more precise audience targeting, many advertisers are wary of TRP and GRP metrics for this medium. According to Joseph Leon, managing director of Internet advertising agency Essence Digital, online advertising increasingly relies on psychographic and exographic profiles for more precise targeting, often to the exclusion of demographics altogether.