Two media plans can cost the same amount and deliver the same number of total impressions—yet perform very differently.
Why? Because impressions do not tell you how many different people you reached or how often those people were exposed. That is why reach and frequency are two of the most important concepts in media planning.
What is reach?
Reach is the number or percentage of people in a defined audience who are exposed to a campaign at least once during a given period.
If your target audience contains 100,000 people and the campaign reaches 60,000 unique people, the campaign has 60% reach.
What is frequency?
Frequency is the average number of times the people reached are exposed to the campaign.
If those 60,000 people generate 180,000 impressions, the average frequency is 3.0. That does not mean every person saw the ad exactly three times; it is an average across those reached.
What are GRPs?
Gross Rating Points, or GRPs, express the total weight of a campaign relative to the audience universe. A commonly used relationship is:
GRPs = Reach × Frequency
This relationship is useful because it shows why the same total campaign weight can be distributed in different ways. A plan can emphasize broader reach with lower average frequency, or concentrate more exposures among a smaller audience.
Which matters more?
Neither wins automatically. The right balance depends on what the campaign needs to do.
A new product launch may prioritize broad reach so more potential customers become aware of it. A short promotional campaign may need enough frequency within a tighter time period for the offer to register. A mature local brand may already have awareness and use frequency differently from a brand entering the market.
Why more frequency is not always better
Repeated exposure can help a message become familiar, but there is a point where additional impressions may add less value. If a plan keeps serving ads to the same small group while large portions of the target remain unreached, the campaign may be inefficient.
Why reach alone is not enough
The opposite problem also exists. A plan may technically reach a large audience, but if most people encounter the message only once, the campaign may not create enough opportunity for the message to be noticed and remembered.
THE SIMPLE TAKE
The goal is not maximum reach or maximum frequency. It is the right balance for the objective, budget, creative and buying window.
A simple example
Imagine two plans targeting 100,000 people.
Plan A reaches 80,000 people at an average frequency of 1.5. Plan B reaches 45,000 people at an average frequency of 4.0.
Plan A creates broader awareness. Plan B creates more repetition among fewer people. Neither is automatically superior. The decision depends on the job the advertising needs to do.
Where CPM fits
CPM measures the cost of delivering one thousand impressions. It is a useful efficiency metric, but a low CPM does not guarantee a strong plan. Cheap impressions delivered repeatedly to the wrong audience—or in a weak environment—can still be poor value.
Questions to ask when reviewing a media plan
• What percentage of my target audience will we reach?
• What is the expected average frequency?
• Over what period will that frequency build?
• Are impressions concentrated too heavily among a small group?
• How much duplication exists across channels?
• Does the creative need repetition to communicate the message?
• Are we optimizing for the business objective or simply for the cheapest CPM?
Bottom line
Impressions tell you how much advertising was delivered. Reach and frequency help explain how that delivery was distributed across people.
Understanding that difference makes it much easier to compare media plans intelligently—and much harder to be impressed by a giant impression number with no context.
Want a second opinion on the reach and frequency in your media plan? Ask Simple.
Sources / reference material
Radio Connects — Media Formulas (reach, frequency, GRPs, CPM and CPP)
https://radioconnects.ca/everything-audio/formulas/
thinktv — Research and TV planning resources
https://thinktv.ca/research/