Target Rating Point is a means of determining how often an advertisement is seen by a specific target audience. Calculating TRP will not indicate an advertisement's effectiveness, but it will give an idea of the amount of exposure an advertiser is getting with its target audience.

Use this formula to determine TRP: TRP = GRP x Percentage of target audience

Determine the numbers. For example, an ad airs with 43 percent of viewers seeing it each of three times it aired. The target demographic is 20 percent of the total audience.

Find the GRP, which is rate x frequency. In the above example, the rate of viewers (43 percent) x the number of times it is seen (three) = GRP. 43 x 3 = 129 gross rating points.

Plug the GRP into the formula. GRP (129) x target audience percentage (20 percent) = TRP. 129 x .20 = 25.8 target rating points.

Interpret the numbers. Generally, TRP should average between 100 and 300 per week. Extremely good would be 400 or more, and less than 100 is ineffective. The score of 25.8 in this example shows an ineffective ad campaign.