Calculate the viral k-factor and whether growth is self-sustaining.
A k-factor above one means each user brings more than one replacement, producing compounding growth. Below one the effect is a finite multiplier on acquisition rather than growth in its own right, summing to 1 ÷ (1 − k). Sustained k above one is extremely rare, so most products treat virality as a multiplier that lowers effective acquisition cost rather than as a growth engine.
Viral Coefficient
k = invitations per user × invitation conversion rate
k = invitations per user × invitation conversion rate A k-factor above one means each user brings more than one replacement, producing compounding growth. Below one the effect is a finite multiplier on acquisition rather than growth in its own right, summing to 1 ÷ (1 − k).
Sustained k above one is extremely rare, so most products treat virality as a multiplier that lowers effective acquisition cost rather than as a growth engine.
This calculator takes 5 inputs: Invitations sent per user, Invitation conversion rate, Viral cycle time, Starting users, Projection window. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.