The definition, calculation method, and points to note for those who are too embarrassed to ask about GRP

Update date: 2025.12.01 Column

GRP is an abbreviation for Gross Rating Point, and means "total viewer rating." It is a term commonly used by advertising and marketing departments and advertising agencies who run TV commercials, but it is not a word that is generally familiar to the general public. Also, because it is a simple concept, it seems that there are surprisingly many people who only have a vague understanding of it.

Have you ever been talking to a colleague at work or an ad agency employee and thought, "Huh? Something's not right? We're not on the same page." This article is for people like you, and will introduce some basic knowledge about GRP, including its definition and how to calculate it.

After reading this article, you will have a clear understanding of GRP terminology and will no longer be left wondering, "Oh, is that what it means?"

If you would like to quickly get an overview and some points to note rather than going into the details, please take a look at "GRP for Busy People"! We hope this article will help you gain a solid understanding of GRP and related knowledge, and use it to your advantage in the future.

table of contents

GRP for busy people
Basic knowledge of GRP
- What is GRP?
- Individual and household viewership ratings
How to Calculate GRP
Points to note when considering advertising effectiveness from GRP

GRP for busy people

GRP is an abbreviation for Gross Rating Point, and refers to the cumulative viewer rating. GRP is calculated based on "household viewer rating," and is calculated by measuring the "household viewer rating during the time period (xx:xx) when a commercial is aired" each time a commercial is aired, and adding up the household viewer ratings over a certain period. The household viewing rate indicates what percentage of households in the surveyed area "were tuned in to the channel on which the commercial was aired." There are two methods for surveying household viewer rating: the "people meter (PM) system" and the "online meter system." Both systems measure once per minute which channel was being displayed on the televisions (maximum of 2 units) in the surveyed households. When considering what the acquired GRPs (called actual) bring to advertisers, it is important to consider "What impact did TV commercials have on customer numbers and sales/profits?It is important to think from this perspective. It is easy to make intermediate indicators such as awareness and favorability the only goal, but companies that select intermediate indicators and implement the PDCA cycle while considering how they affect final results continue to be successful.

Basic knowledge of GRP

What is GRP?

GRP is an abbreviation for Gross Rating Point, and means the total viewer rating. GRP is the total "household viewer rating" of TV commercials aired during a specific period. It is important to note that this is only the total household viewer rating, and that the areas in which they are broadcast are limited. If TV commercials are replaced with web ads, GRP becomes an indicator similar to IMP (impression).

It is mainly used to decide the desired level of exposure in contracts for spot commercials (commercials where the commercial slot in a specific program cannot be specified).It takes the form of something like, "We invested 1,000 GRPs in the last campaign, but we still have some reach (reach rate: what percentage of households saw the commercial), so we would like to invest 2,000 GRPs this time."

Individual and household viewership ratings

Viewer ratings are divided into two types: "individual viewership ratings" and "household viewership ratings." Naturally, the calculation methods, survey methods, and implications of each are different, so it is important to understand them accurately. Individual viewership ratings are calculated by classifying individuals in the households surveyed for viewership ratings by gender, age group, occupation, etc. The detailed calculation method will be described later, but it is calculated based on how many people in each characteristic category in the entire surveyed household were watching. For example, if there are 2 people in the F1 demographic (women, 20-34 years old) in the entire surveyed household, and 10 of them are watching the program, the individual viewership rating is 5% (50 viewers ÷ 5 total people).

Household viewership rate refers to how many households out of all households surveyed watched the program. To be more precise, it does not measure whether or not they were watching, but whether or not the TV was on, so it is important to note that it cannot be said that people were watching the program. The viewership rate that is generally referred to refers to this household viewership rate.

The household viewer rating is also the subject of GRP calculations. Viewer ratings are surveyed by Video Research, Inc. using three methods: the People Meter (PM) System, the Online Meter System, and a Diary-Style Survey.

Surveys using the People Meter system are carried out using a device called a People Meter, which is installed on the televisions (up to 8 units) of the surveyed households. Two things are measured: "the channel displayed on the screen of the television where the People Meter is installed" and "the people watching television." Each person in the surveyed household presses a button that says "I'm watching!" to tell the People Meter who is watching that television. In other words, it is a system that simultaneously surveys household and individual viewer ratings.

(※ I have never actually used the people meter, so this is unconfirmed information, but it seems that an alert will sound if a TV program is being displayed even if no button to tell people who is watching has been pressed.)

Surveys using the online meter system are conducted using channel sensors installed on the televisions (up to 8 units) of the surveyed households. The channel being measured is the channel displayed on the screen of the television on which the channel sensor is installed. The household viewer ratings are surveyed based on which channel each television in the surveyed household was showing.

A diary-style survey is conducted by an investigator who visits the households and distributes questionnaires. It measures TV viewing habits every day for one week. Unlike the two survey methods mentioned above, there is a space to write answers in 1-minute increments, and this is used to measure individual viewer ratings.

Until now, commercials were purchased based on GRP calculated from household viewer ratings, but from April 2018, commercials will be purchased based on GRP calculated from individual viewer ratings (Kanto region).

How to Calculate GRP

GRP is the total household viewer rating. You can calculate GRP by adding up the viewer ratings for commercials aired within a certain period of time. For example, let's consider the following scenario.

The ad airs once a day from Monday to Friday.
The viewer ratings for each commercial broadcast time slot (minutes)
The results were 5%, 5%, 10%, 10%, and 8%.

GRP during this period is 28% (5% + 5% + 10% + 10% + 8%).

Points to note when considering advertising effectiveness from GRP

To put it bluntly, it is extremely dangerous to judge a campaign as a success or failure solely based on how many actual GRPs it gained and how much its brand awareness increased.

In today's world, where customer behavior is complex and difficult to visualize, it is becoming increasingly difficult to achieve results through advertising. If you cannot quantitatively evaluate how much sales increased or how much profit was generated as a result of placing an ad, you will not be able to implement the PDCA cycle or implement appropriate improvement measures, and the effectiveness of your advertising will be difficult to improve.

Many companies that run TV commercialsAdvertising effectiveness is an intermediate indicator of awareness and favorabilityHowever, very few companies disclose the extent to which these intermediate indicators have influenced final performance indicators such as sales and profits.How will it impact other marketing initiatives?""FinallySales, profits, ROI (return on investment)Unless you clarify the extent to which the number of viewers will increase, you won't know how many TV commercials you need to run in order to achieve your goal, or what type of TV commercials you should run.

Over the past one or two years,Quantify the impact of TV advertising on the bottom lineThere are a lot of services popping up, and if you're not already using one of them, I'd recommend you consider it!