GRP (gross rating point)
The classic currency of broadcast reach: one GRP equals reaching 1% of the target audience once, so GRPs = reach x frequency. TRPs are the same arithmetic against a specific target group. A campaign at 80% reach and 3 average frequency delivered 240 GRPs.
Where it's used
Used in TV, radio and outdoor planning and buying. Good for comparing campaign weight across markets. It says nothing about how the weight is spread.
How to calculate it
GRPs = Reach % × Average frequency
Worked example
Illustrative numbersYou compare two TV schedules. Plan A reaches 75% of the target four times on average. Plan B reaches 50% of the target six times.
Plan A
75 reach × 4 frequency = 300 GRPs
Plan B
50 reach × 6 frequency = 300 GRPs
What it tells you
Both show 300 GRPs, yet A reaches 50% more people. For a brand after new buyers, these are not the same purchase.