# Know-How Exchange

## Topic: Other

Search more Know-How Exchange Q&A from Marketing Experts

This question has been answered, and points have been awarded.

### Calculating Reach, Frequency And Grp For A Campain

Posted by Anonymous on 125 Points
Hi, if I am putting together a campaign sing multiple media I understand I need to calculate the GRP for each separate item ie tv, reach 50 frequency 3 GRP 150 and magazine reach 40 frequency 4 GRP = 160. How do I then present this information for the total campaign do I leave the information separate for each media type or add it together in some way to present a final calculation? Many THanks

• Posted by mgoodman on Accepted
You *can* combine GRPs, but it's not typically done ... and it's very difficult to even estimate combined reach or combined frequency because there is very little hard data about overlaps. ("Of the people who see my TV ad, how many also read the print media I'll be using?")

Theoretically, you could calculate the extremes: everyone who sees a print ad also sees the TV ad, so the GRPs only contribute to frequency, not reach; and everyone who sees a print ad is a different person from everyone who sees a TV ad, so GRPs contribute only to reach, not frequency.

What you have to be sure of is that the base size for your GRPs is the same. Remember that GRPs are based on a percentage (i.e., reach = % of population you reach). If the "population" is different for different media, then you can't really combine GRPs. That's why it isn't usually done.

There are algorithms that some large agencies use that will estimate combined GRPs, but they're pretty flaky, and many sophisticated clients won't look at them.

Hope this helps. There may be a media maven here who can do a better job of answering this question than I did! :)