OOH glossary · Measurement
Gross rating points (GRP)
Gross rating points (GRPs) measure campaign weight: in-market impressions as a percent of the market’s population.
Geopath defines GRPs as a schedule’s in-market impressions, shown as a percent of the market population. One GRP equals impressions equal to 1% of the population.
OAAA best practice shows market GRP levels of 100, 150, 200, 250 and 300. Posters are often sold in GRP packages.
GRPs can top 100 because the same people are counted more than once.
Formula
GRPs = (in-market impressions ÷ market population) × 100. Also, GRPs = reach (%) × frequency.
Example
Say a market has 200,000 people (an example figure). A four-week poster package delivers 400,000 in-market impressions. GRPs = 400,000 ÷ 200,000 × 100 = 200.