Reach & Frequency Calculator
Work out how many unique people a buy can reach at a given frequency cap, what it costs per person, and whether the audience is even large enough to absorb the impressions. The result is a ceiling rather than a forecast, and the page is explicit about why.
For cost per unique user.
How many people the targeting can actually reach.
Enter impressions and a frequency cap to estimate reach.
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Formula
Impressions = Reach × Frequency · Maximum Reach = Impressions ÷ Frequency Cap · Cost per Unique User = Spend ÷ ReachThe first identity is exact and the others follow from it. What is not exact is the assumption behind them — that impressions distribute evenly across users up to the cap. That assumption is optimistic, which is why the output is described as a maximum.
Why the honest answer is a ceiling
Reach and frequency multiply to impressions, and that relationship is exact. What is not exact is how impressions distribute across people. Audience visit frequency is heavily skewed: a small minority of users account for a disproportionate share of available impressions, so a campaign delivering an average of four impressions per person is rarely delivering four to everyone. It is delivering twelve to some and one to others. A frequency cap trims the top of that distribution, but it cannot manufacture new people to spend the trimmed impressions on. That is why every reach forecast that claims precision is either modelling a specific audience distribution or quietly guessing, and why this one reports a bound instead.
Saturation is the failure this catches
The most common way a reach campaign underperforms is not a bad cap but too small an audience. When targeting narrows to a few tens of thousands of people and the budget buys millions of impressions, the arithmetic has nowhere to go: once everyone has hit the cap, further delivery either stops or pushes frequency past the limit. Both outcomes are bad and both look like something else in reporting — under-delivery in one case, an unexplained frequency breach in the other. Entering an addressable audience size here surfaces the problem before the campaign runs, which is the only point at which it is cheap to fix.
Frequently asked questions
- Why is this an upper bound rather than a forecast?
- Because it assumes impressions spread perfectly evenly across users up to the cap, and they never do. Visit frequency is heavily skewed — a small share of users generate a large share of impressions — so in practice the heavy users hit the cap early while light users are reached once or not at all. Real reach lands below this number, and how far below depends on the publisher's audience, which is not knowable from these inputs.
- What does it mean when the audience is saturated?
- It means the buy has more impressions than the targeted audience can absorb at your cap. Those extra impressions do not find new people; they raise average frequency above the cap you set, which is exactly what the cap existed to prevent. The fix is to widen targeting or move budget, not to adjust the cap.
- What is a sensible frequency cap?
- It depends entirely on the objective and the flight length, so treat any published number with suspicion. What is worth doing is checking the implied trade-off here: halving the cap doubles the maximum reach for the same money, but only if there are enough addressable people to reach. Where the audience is small, a lower cap simply leaves impressions unbought.
- Why is cost per unique user more useful than CPM here?
- Because CPM prices impressions and reach campaigns buy people. Two buys at the same CPM can differ several-fold in cost per unique user if one runs against a narrow audience that saturates. When the objective is reach, cost per unique user is the number that actually compares two options.