The reach of an advertising campaign is the estimated number of customers that will be exposed to the products of the campaign within a predetermined time period. Reach can be given as a number or as a fraction of a certain group such as "women" or "men aged 25-35".

What qualifies someone being exposed to advertising differs depending on the type of media it is. For example, in the UK BARB defines the reach of a television channel as the percentage of the population in private households who view a channel for more than 3 minutes in a given day or week.