Viral Coefficient

The viral coefficient measures how many new users one current user generates on average through invitations. It works by multiplying the number of invites each user sends by the fraction of those invites that turn into sign-ups, so it captures both outreach volume and effectiveness. If the result is above 1, each user brings in more than one new user on average, which can support rapid growth; if it is below 1, growth from referrals alone will eventually slow.

Use this when analysing referral programs, invite-only products, or word-of-mouth growth in apps, games, and subscription services. It is especially useful for estimating whether user-driven sharing can sustain acquisition without heavy paid marketing.

• Using the total number of sign-ups instead of the average sign-ups per user
• Entering the conversion rate as 12.5 instead of 0.125
• Assuming a high invitation count alone means viral growth, even if the conversion rate is low