Definition: Virality rate is the percentage of impressions on a post that led to a share, showing how likely people who saw the post were to pass it on.
Also called: share rate
Updated October 11, 2026
Virality rate = shares ÷ impressions × 100Most definitions divide by impressions; some divide by reach, which reads slightly higher because it counts each person once. Neither is wrong. Pick one, say which one you used, and keep it the same so month-on-month numbers stay comparable.
Virality rate measures how share-worthy a post was to everyone who saw it, including non-followers. Amplification rate divides shares by followers and measures how willing your own audience is to share. A post can have a high virality rate on a small reach and still a low amplification rate.
An X post earns 25,000 impressions and 175 reposts. Virality rate = 175 ÷ 25,000 × 100 = 0.7%.
Amplification rate is the number of shares a post receives relative to your follower count, showing how often your audience passes your content on to their own networks.
Impressions are the total number of times a post was displayed on screen, counting repeat views by the same person.
Engagement rate is the percentage of people who interacted with a post (liked, commented, shared, saved or clicked) out of the people who saw it or follow the account.
Organic reach is the number of unique people who saw a post or account through unpaid distribution (feeds, search, shares and recommendations), excluding anyone reached through ads.
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