Reach and Frequency Calculator
From impressions and the size of the audience, the share of people a campaign reaches at least once, how many times the average person sees it, the rating points delivered, and what a target frequency would need.
Impressions divided by audience is the average frequency if everyone were reached — but they are not.
How the reach and frequency calculator works
Impressions divided by audience is the average frequency if everyone were reached — but they are not. Some people see the ad five times and some never, and the standard estimate assumes exposures land at random: reach is one minus e to the minus impressions-per-person. Reach times frequency is the gross rating points, the currency media is bought in, and the effective reach at a target frequency is what a brand campaign actually plans against.
Formula: GRPs = impressions / audience × 100; reach ≈ 1 − e^(−impressions / audience); frequency = impressions / reached
Worked examples
| Inputs | Reach (share of audience seeing it at least once) | Note |
|---|---|---|
| 2.4 million impressions on 800,000 people | 95.02% | 95% reach, frequency 3.2 |
| A light campaign | 39.35% | 39% reach |
| A high target frequency | 95.02% | far more impressions needed |
FAQFrequently asked questions
What is the difference between reach and impressions?
Impressions count every exposure; reach counts people exposed at least once. The gap between them is frequency — the same people seeing the ad again.
What are GRPs?
Gross rating points: impressions as a percentage of the audience, or reach times frequency. 300 GRPs can be 100% reach at 3 or 50% at 6; the split is the media plan.
Why the Poisson estimate?
It assumes exposures land on people at random, which is a fair first approximation for broad media. Targeted digital buys concentrate exposures, so real reach is lower and frequency higher than this estimate.
What is effective frequency?
The number of exposures a message needs before it works — three is the traditional planning figure for awareness. Effective reach is the share of the audience that gets there.
Why does reach saturate?
Because once most people have seen the ad, further impressions land on them again. Beyond about 300 GRPs, spend buys frequency rather than new people.
Where these figures come from
- Interactive Advertising Bureau — measurement guidelines — the impression and viewability definitions CPM depends on
- Advertising Standards Authority — the UK advertising regulator
Last checked: September 2026. These are standard industry definitions; where platforms disagree, the page says so.