The formula, and the two versions of it
The follower-based version is the common one: (likes + comments + saves + shares) divided by follower count, multiplied by 100. A creator with 20,000 followers whose posts average 400 likes, 40 comments, and 60 saves has an engagement rate of 500 divided by 20,000, which is 2.5 percent.
The reach-based version replaces followers with the number of accounts that actually saw the post. It's more honest, because it ignores dormant followers, but you can only get it from the creator's own analytics. When a creator quotes an engagement rate, ask which denominator they used. Some tools count only likes and comments; others include saves and shares. Compare like with like.
What it tells you, and what it doesn't
Engagement rate is a proxy for how much an audience cares about a creator's posts. It's most useful when you're paying for reach, because a large following with almost no interaction usually means bought followers or a disengaged audience. As a rough convention, smaller accounts post higher rates than large ones, so judge a creator against peers of similar size, not against a single benchmark.
It says nothing about whether the content will sell your product. Comments can be friends and bots. High-engagement accounts are often entertainment accounts whose followers don't buy anything. It also doesn't measure how the same creator's content performs as an ad, which is a separate question answered by hook rate and conversion data.
Why it matters less for UGC creators
When you hire a UGC creator to make content for your own channels and ads, their audience never sees the video. Their engagement rate is almost irrelevant. What matters is whether they can hold attention on camera, follow a brief, and deliver on time. A creator with 900 followers and no engagement to speak of can still produce your best-performing ad.
Use engagement rate as a fit signal for influencer-style deals where you pay for their reach, and as a light sanity check on creators generally. For production deals, weight past work, niche match, and responsiveness ahead of it.
How it's used
Sourcing note: "Shortlist creators between 5k and 50k followers with an engagement rate above the median for their size, then screen for on-camera quality."
Creator reply to a brand: "My engagement rate is around 4 percent by followers, about 9 percent by reach; happy to share a screenshot of the last 30 days."