Reach is the number of unique accounts that saw a post, impressions is the total number of times it was shown including repeats. You do not calculate them by hand, the platform analytics reports both. Impressions are always equal to or higher than reach.
My report has reach and impressions and I am not sure of the difference or where they come from. How do you calculate reach and impressions?
Reach is unique people, impressions is total views including repeats. The platform reports both, you do not work them out yourself.
Watch the gap between them. Impressions way above reach means the same people saw it several times, which is not the same as broad reach.
These two are not really calculated, they are reported by the platform but understanding the difference is what matters. Reach is the count of unique accounts that saw your content. Impressions is the total number of times it appeared on a screen, including the same person seeing it more than once. So impressions are always equal to or greater than reach.
Where to find them: every business or creator account on Instagram, TikTok and the rest reports both in its native analytics per post. The ratio between them is the useful bit. Impressions far above reach means a smaller group saw it repeatedly, which can signal strong saved or shared content, while reach close to impressions means a wide single-pass audience.
Reach is also the more honest denominator for an engagement rate, since it reflects who actually saw the post rather than your whole follower count. Flinque uses real audience and engagement data on creator profiles, so the reach behind a creator influence is visible rather than guessed.
For engagement rate, reach is the fairer denominator than followers. It counts who actually saw the post, not who might have.