Reach is a measurement of the size of the audience to whom you will communicate (or to whom you have communicated) with your advertising schedule.
It is the total of the readers, listeners, viewers or surfers of every medium in which you will run (or have run) an ad or commercial.
Media planners use it as one of their planning tools. They try to balance it with Frequency (number of exposures) and do it all within the allotted budget.
How You Do It
Resources available to help in your calculation include rate cards from specific outlets and directories such as Cision and SRDS and Alexa.
After the fact, it is a measurement for reporting and analysis. It is a permanent record of where your advertising messages went.
Some advertising people also factor in a “pass-along” rate. The pass-along rate is the number of people who see each issue, including the subscriber/purchaser and every other person his copy is passed to before it is discarded. Estimates of pass-along rates run as high as 5 (five readers per copy).
So, a magazine that has a circulation of 500,000 and that claims a pass-along rate of 5 would have a presumed total readership of 2.5 million. Often a magazine will state these numbers on its rate card. However, many advertising people are skeptical of pass-along rates and do not factor them into their calculations.
This is a fundamental navigational metric. Combined with Frequency, it is the basic measurement of how you communicated with your target audience.
By itself, it provides no analysis – for example, it provides no evaluation of a publication’s credibility with the audience. It is important not to make this metric do more than it is meant to do.