Gross rating point
Gross rating point (GRP) is a term used in advertising to measure the size of an audience reached by a specific media or schedule. Specifically, GRPs quantify impressions as a percentage of the population reached rather than in absolute numbers reached. Target rating points express the same concept, but with regard to a more narrowly defined target audience.
GRPs are used predominantly as a measure of media with high potential exposures or impressions.
The purpose of the GRP metric is to measure impressions in relation to the number of people in the audience for an advertising campaign. GRP values are commonly used by media buyers to compare the advertising strength of various media vehicles.
- GRPs (%) = Reach (%) × Average frequency (#)
A television advertisement that is aired five times reaching 50% of the audience each time it is aired would have a GRP value of 250 (5 × 50%). To achieve a common denominator and compare media, (reach × frequency) are expressed over time (divided by time) to determine the 'weight' of a media campaign.
Alternatively, GRPs may be calculated in relation to the number of impressions:
- GRPs (%) = 100 * Impressions (#) ÷ Defined population (#) 
- Farris, Paul W.; Neil T. Bendle; Phillip E. Pfeifer; David J. Reibstein (2010). Marketing Metrics: The Definitive Guide to Measuring Marketing Performance. Upper Saddle River, New Jersey: Pearson Education, Inc. ISBN 0-13-705829-2. The Marketing Accountability Standards Board (MASB) endorses the definitions, purposes, and constructs of classes of measures that appear in Marketing Metrics as part of its ongoing Common Language: Marketing Activities and Metrics Project.
- American Marketing Association Dictionary. http://www.marketingpower.com/_layouts/Dictionary.aspx. Retrieved 2013-2-11. The Marketing Accountability Standards Board (MASB) endorses this definition as part of its ongoing Common Language: Marketing Activities and Metrics Project.
- "GRP defined". Ad Vision Outdoor. Retrieved March 12, 2012.
- "Gross Rating Points (GRPs)". Marketing Metrics Made Simple. Retrieved March 12, 2012.