What Is Viral Coefficient?

The number of new users each existing user generates through referrals or sharing.

The viral coefficient (K-factor) measures how many new users each existing user brings in through referrals, invitations, or word-of-mouth. A coefficient above 1.0 means viral, self-sustaining growth.

Few SaaS products achieve a true viral coefficient above 1.0. Even a coefficient of 0.3-0.5 can significantly reduce acquisition costs by supplementing paid channels with organic growth.

To increase virality, build sharing into the product experience (collaborative features, public pages, invite flows) rather than relying on external referral programs alone.