The Viral Coefficient is a metric that measures the number of new users generated by an existing user through referrals or product loops. It is the math behind 'Organic Growth' and 'Word of Mouth.' The coefficient is calculated by multiplying the number of invitations sent per user by the conversion rate of those invitations. A Viral Coefficient greater than 1.0 means that the product is growing exponentially on its own; for every 10 users you acquire, they will bring in 11 or more additional users. A coefficient below 1.0 means growth is linear and requires a constant 'pump' from paid marketing or sales. True virality is rare and is usually built directly into the product’s utility—for example, a collaboration tool like Slack or a payment tool like PayPal naturally requires you to invite others to get value. Increasing the Viral Coefficient involves reducing the friction of the invite process and creating incentives that encourage users to share the product with their network.