Viral coefficient (K-factor) determines whether your product can achieve exponential organic growth or requires continuous paid acquisition. K > 1.0 means each user brings more than one additional user, creating exponential growth without ad spend. K = 0.7 means 10,000 users generate 7,000 referred users, who generate 4,900 more - powerful supplement to paid channels but not self-sustaining. K < 0.3 provides minimal organic growth, requiring heavy reliance on paid acquisition. Most products achieve K = 0.2-0.5 without optimization.

Improving viral coefficient can transform economics. Higher K-factors generate substantially more viral users from the same paid acquisition base. For a company spending significantly on acquisition, increasing K-factor can add substantial organic customers representing considerable value in avoided CAC.

Viral growth compounds faster with shorter viral cycle time. Products with shorter cycle times can grow substantially faster than those with longer cycles at the same K-factor. Consumer apps with in-product sharing can achieve very short cycle times. B2B products with email referrals typically see longer cycles. Enterprise with sales-assisted referrals generally run even longer cycles. Optimizing both K-factor and cycle time creates viral flywheels that can dramatically reduce dependency on paid channels.