What is Ad frequency?
Ad frequency is the average number of times each person in your audience saw your ad: impressions divided by reach.
Formula
Frequency = impressions ÷ reachSome repetition helps people remember an ad; too much makes them ignore it. Frequency climbs fastest in small audiences such as retargeting lists.
There's no universal right number. Watch frequency against CTR and cost per purchase for the same ad.
Example
1,20,000 impressions across 30,000 people is a frequency of 4.