Gross Rating Points (GRP) is a fundamental metric in advertising and media planning used to quantify the total audience exposure delivered by an entire schedule of advertisements. This single number represents the gross media weight of a campaign. Understanding how to calculate and apply this metric is necessary for media buyers and strategists to compare the delivery of different advertising schedules. This article explains the calculation methods for GRP and discusses its practical applications.
Understanding the Core Components of GRP
The Gross Rating Point is a composite number derived from three foundational metrics that measure how an audience interacts with advertising. These components combine to provide a comprehensive view of a campaign’s overall delivery.
The Rating is the percentage of the target audience exposed to a single placement of an advertisement or program. For example, a Rating of 5 for a specific television show means that 5% of the intended audience watched that program when the advertisement aired. This metric is the base unit of audience measurement for a single media event.
Reach refers to the percentage of the target audience exposed to the advertising message at least one time during the entire campaign period. It tracks the unique individuals or households who encounter the ad, counting a person only once regardless of how many times they see the commercial. Frequency is the average number of times the reached audience was exposed to the advertising message during the campaign.
Calculating GRP Using Reach and Frequency
The most common conceptual method for determining Gross Rating Points involves a simple multiplication of two core audience delivery metrics. GRP is calculated by multiplying the percentage of the target audience reached by the average number of times they were exposed to the advertising. The formula is expressed as: GRP = Reach (%) x Frequency.
Consider a national advertising campaign. If the media schedule successfully exposes 75% of the target audience (Reach = 75) and that audience saw the advertisement an average of 4 times (Frequency = 4), the GRP is 300.
While Reach is expressed as a percentage, the resulting GRP figure is presented as a whole number. GRP signifies the total weight of the advertising delivery and accounts for duplicate exposures, meaning it can, and often does, exceed 100. A campaign with a GRP of 150 could mean 50% of the audience was reached an average of 3 times, or 75% was reached an average of 2 times. This methodology allows media planners to quickly summarize the total impact of a schedule in a single, easily comparable figure.
Calculating GRP by Summing Individual Ratings
An alternative and equally valid method for calculating Gross Rating Points involves summing the ratings of every individual advertisement placement within the media schedule. This method is often the more practical approach for media buyers, as they receive the audience rating for each specific program or time slot purchased. The formula is simply: GRP = Sum of all Individual Ratings.
For example, a media plan might include four different commercial spots scheduled over a week. If the spots achieve Ratings of 12, 15, 10, and 8, the total GRP for the weekly schedule is 45.
This calculation demonstrates how GRP represents the accumulation of audience exposure across the entire media buy. While the Reach x Frequency method is conceptual, the sum of ratings method is a direct, post-buy calculation that confirms the actual delivery of the campaign spots. Mathematically, both methods measure the exact same total advertising weight, providing a way to both plan the media schedule and verify the delivered audience exposure.
Strategic Application of Gross Rating Points
Once Gross Rating Points are calculated, the metric serves several functions in media planning and campaign management. GRP provides a standardized measure that enables advertisers to compare the weight and size of entirely different media schedules. A planner can use GRP to evaluate whether a proposed schedule of radio spots delivers a comparable amount of total audience exposure to a schedule of digital video advertisements.
GRPs are also used to set concrete campaign goals and establish performance benchmarks. For instance, a brand might determine that a new product launch requires a minimum of 400 GRPs over a four-week period to generate sufficient market awareness. This target GRP then informs the entire media buying process, guiding the allocation of budget across various channels.
The metric is also fundamental to budgeting through the calculation of the Cost Per GRP (CPGRP). This is determined by dividing the total cost of the media schedule by the total GRPs delivered. The resulting figure indicates the cost to achieve one rating point, allowing media buyers to assess the cost-efficiency of different media vendors or platforms.
Key Limitations of Using GRP
While Gross Rating Points serve as a standard measure of media weight, the metric has limitations because it focuses only on gross exposure, not effectiveness. GRP calculates the total audience exposure, which inherently counts duplicate exposures, meaning the same person seeing the ad multiple times contributes to a higher GRP score. This gross measurement does not distinguish between a campaign that reaches a wide audience once and one that reaches a smaller audience multiple times.
GRP also does not provide insight into the quality of the exposure delivered by the advertising. The calculation does not account for factors such as the viewability of an advertisement, the clutter of surrounding ads, or the emotional context of the content in which the ad appears. Consequently, a high GRP does not guarantee that the audience paid attention to the advertisement.
Furthermore, GRP is not designed to measure the optimal level of exposure needed to influence a consumer, known as effective frequency. It is simply a volume measure that cannot indicate whether the audience saw the ad too few or too many times to prompt an action. GRP is a measure of media delivery, and it has no direct correlation to business outcomes such as sales results, brand lift, or return on investment.