Occasionally, media buyers are presented with circulation information outside of the format they need for a particular application. Both Gross Impressions (GI’s) and Gross Rating Points (GRP’s) are frequently used to compare different options against each other or to evaluate an entire advertising budget across multiple media types. Media Link Software™ (MLS) does use these sorts of calculations on the schedules you build within the software, but buyers should be familiar with the formula in order to be prepared for scenarios where you require quick “napkin” evaluation. You only need two out of three factors- Gross Impressions, GRP’s, and the total market demographic population. We have also seen some people call it the universe or the audience.
Gross Impressions: A count of individuals be exposed to an ad one time.
Gross Rating Point: A number representing the same number of impressions as reaching 1% of the market demographic population. Many GRP’s may be summed together even in excess of 100% in order to evaluate the entire value of an ad placement or group of them.
Market Demographic Population: The number of people with defined characteristics you could conceivably reach with this campaign (i.e. all the women 25-54 in a given city).
Impressions to GRP’s
Gross Impressions = (GRP’s/100) x Market Demographic Population
GRP’s to Impressions
GRPs = (gross impressions / market demographic population) x 100.
Let’s say you want to compare advertising you have done in movie theaters to the TV schedule you are running simultaneously. Professional broadcasters will demonstrate their reach via GRP’s, but the movie theaters provide you with impressions data. So, let’s say you know you have defined your target market to consist of 500,000 people and you know in a given week the theater vendor estimates 250,000 impressions.
First divide Impressions by the population. In this case, that would be 0.5. Then, multiply by 100 and you have your GRP number or 50. You now can factor your understanding of what your video ads are doing across your different delivery platforms.