Glossary

Viral coefficient

The average number of new users each existing user brings in, used to measure whether growth is self-sustaining.

The viral coefficient measures how much a product or piece of content grows through its existing users bringing in new ones, expressed as the average number of new users or viewers each existing user generates.

It is calculated as k = i x c, where i is the number of invitations or shares sent per existing user and c is the conversion rate of those invitations into new users. A viral coefficient above 1 means each user generates more than one new user on average, producing self-sustaining, compounding growth; below 1, growth requires continued outside input such as paid acquisition or fresh content velocity.

Product and growth teams track the viral coefficient alongside follower growth rate and other north star metrics to distinguish organic, referral-driven growth from growth bought through advertising, and it is central to product-led growth strategy. The main pitfall is measuring it over too short a window or too small a user base, producing a volatile estimate, and confusing a high viral coefficient with high overall growth when the total user base feeding the loop is still small.

Last reviewed September 22, 2026

In the index now

Related terms

Content velocity The rate at which an organization or creator publishes new content over time, tracked to sustain audience growth and visibility. Follower growth rate The percentage change in an account's follower count over a period, used to track audience-building momentum on social platforms. Product-led growth (PLG) A go-to-market approach where the product itself, often via free trials or freemium use, drives acquisition and expansion. North star metric The single metric a team chooses as the best proxy for the core value a product delivers to customers. Referral traffic Visits that arrive by clicking a link on another website, other than a search engine, paid ad or social network.