What is a gross rating point?

Gross rating point is the term used by marketers to measure the size of an advertising campaign by a specific medium or schedule. Gross rating point quantifies impressions as a percentage of the target population. This percentage can be greater than 100. Gross rating point is used predominantly as a measure of media with high potential exposures or impressions. GRP is used by media buyers to compare the advertising strength of components of a media plan.