A Gross Rating Point, or GRP, is a measurement of audience size.
GRPs measure the exposure to one or more programs or commercials, gauging the total volume of delivery.
Rating points are KPIs specific to media planning and media buying. A rating point is a metric that measures the size of an audience reached through a specific media channel. It communicates the percentage of people (or households) tuned into a program, compared to the population (or population of households).
In other words, Gross Rating Points are a cumulative measure of the impressions an ad campaign can achieve.
Note: GRPs are not to be confused with TRPs, or Target Rating Points. TRPs measure reach and frequency with a target audience, as opposed to the larger population.
How to Calculate GRPs
GRP = Reach (% of audience reached) x Frequency (number of ad impressions)
Here’s an example:
A campaign delivers an average frequency of 5 impressions to 1,000,000 Millennials (18-34 year-olds), out of an average total population of 70,000,000 Millennials.
GRP = (1,000,000 / 70,000,000) x 5
GRP = 1.43% x 5
GRP = 7.15