What is Viral Coefficient and how is it calculated?
Short Answer
Viral Coefficient is the number of new users each existing user generates through referrals or sharing — values above 1.0 indicate exponential growth potential.
Full Explanation
Viral Coefficient = (Number of Invitations Sent per User) × (Acceptance Rate). If each user shares the app with 3 friends and 20% accept, Viral Coefficient = 3 × 0.2 = 0.6. This means each user generates 0.6 new users. With a 0.6 coefficient, an initial user base of 100 grows to 100 + 60 (from referrals) + 36 (from those 60) + 22 + 13 + 8 + ... eventually reaching a plateau as the market saturates. A Viral Coefficient of 1.0 is the breakeven point — the user base neither grows nor shrinks through referrals. Above 1.0 indicates exponential growth. Instagram and WhatsApp achieved Viral Coefficients of 2.0+, enabling explosive growth with minimal paid acquisition. For most apps, Viral Coefficient is below 1.0 and is supplemented by paid acquisition. Improving Viral Coefficient is often more valuable than paid marketing because it reduces CAC while maintaining LTV. Founders can increase Viral Coefficient by: (1) making sharing easy (built-in referral tools), (2) incentivising sharing (referral rewards), (3) improving acceptance rate (product quality, social proof), or (4) increasing frequency of sharing (notifications, seasonal events).
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