The three common formulas:
- By reach: (total engagements ÷ reach) × 100
- By followers: (total engagements ÷ follower count) × 100
- By impressions: (total engagements ÷ impressions) × 100
These produce very different numbers from the same post, and the one you pick decides whether your rate looks good. Reach-based rates run highest, because reach is the smallest denominator. Follower-based rates fall automatically as your following grows, even when nothing got worse.
Pick one, write it down, and never change it mid-comparison. Most “our engagement dropped” alarms are a denominator change or a platform reporting change, not an audience change.
What the number can’t tell you
An engagement rate is a ratio of reactions to distribution. It says nothing about who reacted — and in B2B that’s the part that decides whether any of it was worth anything. A high rate driven by your own industry is authentic in every respect except relevance, and it will never convert into anything. Attention is not agreement.
So calculate it if you need it for reporting, and don’t steer by it. The useful question is which people responded and what happened next.