Reach and Frequency — what is it?

The number of different people an ad reaches (reach) and the average number of exposures (frequency).

Reach is the number or share of different people who saw an ad at least once in a period; frequency is how many times on average those people saw it. Multiplied together they give the total exposure weight (GRP).

The goal in media planning is enough frequency for the message to be learned without wasting budget on unnecessary repetition.