Reach versus frequency
Reach is how many unique people saw the ad; frequency is how many times, on average, each of them did. Frequency is impressions ÷ reach. A little repetition aids recall; too much burns goodwill and money on people who have already decided.
The saturation signal
When frequency climbs while results fall, you have reached the best-matching people in the audience and are now paying to show the same ad to the same people again. That is audience saturation, and the fix is a new audience or fresh creative, not more budget on the same ad set.
Common questions
What is a good ad frequency?
There is no universal number; it depends on the campaign length, audience size, and creative. Watch the trend: rising frequency with falling CTR and rising CPM is the signal to refresh creative or widen the audience.
How is frequency calculated?
Divide total impressions by reach (unique people). 30,000 impressions to 10,000 people is a frequency of 3.