Target Rating Points (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. Target Rating Points (TRPs), in the case of outdoor billboard advertising, equal the total number of in-market impressions from a target audience delivered by an outdoor or an out of home advertising campaign expressed as a percentage of a market population. Below is a simple example of how to calculate 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 target outdoor advertising households saw your ad 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 ad 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.
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