Viral Coefficient Calculator

How it is calculated

The viral coefficient, or k-factor, is k = i × c / 100. Here i is the average number of invitations each user sends and c is the percentage of those invitations that turn into a new user. The tool shows k with two decimals and a status: above 1 is "Viral growth", below 1 is "Sub-viral", and exactly 1 is "At unity". The new-users figure it shows is the same number as k, because each user is counted as bringing k new users. The invites figure must be zero or more and the conversion rate must be between 0 and 100. The status uses the exact value, not the rounded one. The tool does not include time between invitations.

Common mistakes

• Entering the conversion rate as a fraction (0.15) instead of a percentage (15). The tool would read it as 0.15% and show k near 0.01.
• Using total invites sent by the whole user base instead of invites per user. The first field is an average per user.
• Counting people who clicked an invite as converted. Conversion should be completed sign-ups from invites, otherwise k is overstated.
• Reading 1.00 as proof of break-even. The label "At unity" appears only when the unrounded product is exactly 1; for example 3 invites at 33.3% shows 1.00 yet is Sub-viral.
• Ignoring time. A k of 1.2 with a cycle of several months grows far slower than the same k with a cycle of days, and this tool does not measure that cycle time.