GRP stands for Gross Rating Point. A standard measure in advertising, it measures adverising impact. You calculate it as a percent of the target market reached multiplied by the exposure frequency.Thus, if you get advertise to 30% of the target market and give them 4 exposures, you would have 120 GRP.Now, just like most measures, you have to undestand the limitations of GRPs. standard measure in advertising, it measures adverising impact. You calculate it as a percent of the target market reached multiplied by the exposure frequency.