Engagement rate
The share of an audience that interacts with a post — likes, comments, shares and saves divided by followers or reach, as a percentage.
Engagement rate measures how much of an audience actively interacts with content rather than just scrolling past. The basic formula is interactions ÷ audience × 100, where interactions are likes, comments, shares and saves, and audience is usually either your follower count or the post's reach.
It's the single best quick read on whether content resonates, because it normalizes for audience size — a small account with a high rate is often healthier than a large one with a low one. Engagement rate by reach is typically higher than by followers, since reach excludes followers who never saw the post.