Target Rating Points (TRPs) are related to Gross Rating Points (GRPs). A Target Rating Point (TRP) is one percent of the specifically targeted audience, not the total audience, being reached by an advertisement. That is to say, it is a Gross Rating Point times the ratio of the targeted audience to the total audience.
How You Do It
From sources such as rate cards or SRDS or Cision or Alexa, plus your own marketing research, you calculate the ratio of the target audience to the total audience in each market.
Suppose that your target audience consists of golfers, and that golfers make up ten percent (0.10) of the potential audience of a certain local television station.
As in the Gross Rating Points example, if 25 percent of all targeted televisions are tuned to a show that contains your commercial, you would have 25 GRPs. If, the next time the show is on the air, 32 percent are tuned in, you would have 25 + 32 = 57 GRPs. And so on, cumulatively, through the campaign.
At any point in the campaign, the total TRPs equal the total GRPs times the ratio (0.10) of the target audience to the total audience. So, for example, 57 GRPs equal 5.7 TRPs:
57 x 0.10 = 5.7
This is a fundamental navigational metric. It is a coarse measurement of how you approached your target audience and how you spent your budget.
By itself, it provides no analysis – for example, it provides no evaluation of an outlet’s credibility with the audience. It is important not to make this metric do more than it is meant to do.