Viral Coefficient
Measure how many new users each existing user brings.
Explanation
Viral coefficient measures the viral growth of your product by calculating how many new users each existing user generates through referrals, invitations, or organic sharing. A viral coefficient above 1.0 means organic growth—your users are bringing in more users than you're losing. This is the holy grail of sustainable, low-cost growth.
Real-World Example
If 100 users each invite 0.5 new users who actually sign up, your viral coefficient is 0.5. You need 2 existing users to generate 1 new user. If each user brings 1.2 new users, you have viral growth—your user base will grow exponentially even without additional marketing spend.
How to Apply
Calculate: (Number of invites sent per user) × (Conversion rate of invites) = Viral coefficient. To improve: Make sharing valuable to both sender and recipient, reduce friction in sharing process, give users reasons to share (exclusive content, rewards, social status), timing invites when users are happiest.