Engagement rate
Aussi : ER, Engagement rate by reach, Interaction rate, Taux d'engagement
The ratio of interactions (likes, comments, shares) to reach for a given piece of content, used to gauge how well audiences respond relative to how many people saw it.
What it is
Engagement rate measures how actively an audience interacts with a piece of content relative to how many people encountered it. It is expressed as a percentage: interactions divided by a base (reach, impressions, or followers), then multiplied by 100.
Because absolute counts (10,000 likes) mean little without context, engagement rate normalizes response so you can compare content of very different sizes on a level footing.
The core formula
- Engagement rate by reach = (interactions / reach) x 100
- Engagement rate by impressions = (interactions / impressions) x 100
- Engagement rate by followers = (interactions / followers) x 100
Interactions usually include likes, comments, shares, saves, and clicks, though the exact set varies by platform. Always confirm which base and which interaction types a given number uses, since the same post can show very different rates.
Why it matters
- Quality signal, not just volume. A small audience with high engagement often outperforms a large, passive one.
- Comparability. Lets you benchmark posts, campaigns, channels, and creators of different sizes.
- Algorithm relevance. Most feed ranking systems reward early engagement, so the rate can predict organic distribution.
- Efficiency proxy. High engagement often lowers paid amplification cost.
How it is used in practice
- Content optimization: compare formats (video vs. carousel) to see what earns response.
- Influencer selection: vet creators by engagement rate, not follower count, to avoid inflated or fake audiences.
- Reporting: track trends over time rather than obsessing over a single post.
- A/B testing: hold reach roughly constant and vary the creative.
Caution: engagement rate does not measure business outcomes. High engagement with low conversion can signal entertaining but off-strategy content.
Worked example
A post reaches 20,000 people and collects:
- 600 likes
- 150 comments
- 100 shares
- 150 saves
Total interactions = 1,000.
Engagement rate by reach = (1,000 / 20,000) x 100 = 5%.
If a second post reaches 200,000 people and gets 4,000 interactions, its rate is (4,000 / 200,000) x 100 = 2%. The second post has more raw interactions but the first resonates more strongly per person reached.
Common pitfalls
- Mixing bases (reach vs. followers) across reports.
- Comparing across platforms with different interaction definitions.
- Ignoring negative interactions (hides, unfollows) that some tools omit.