The Multiplier

A viral loop works thanks to the virality multiplier (viral coefficient, k) — how many new users one existing user brings on average. The key question: not 'will they show it?' but 'how many people will they show it to?'

Scenario	Cycle 1	Cycle 2	Cycle 3	Cycle 4	Total
k = 0.5Every 2nd brings 1	100	+50	+25	+13	188
k = 1.0Each brings 1	100	+100	+100	+100	400
k = 2.0Each brings 2	100	+200	+400	+800	1 500
k = 5.0Each brings 5	100	+500	+2 500	+12 500	15 600

Start: 100 users. 'Cycle' = one viral loop iteration.

Real-world examples

~0.7

Calendly — recommends to one person, not everyone converts. Slow but steady growth — a company worth billions.

~1.5

Dropbox — extra space for each invite. Just a few invites were enough to push k past 1.

≫ 1

Hotmail — link signature in every email. Dozens of exposures daily. 12M users in 18 months.

≫ 1

WhatsApp — to message someone, they need the app. But you message dozens of people = invite to your entire contact list.

Takeaway: Don't ask 'will they show it?' Ask: 'How many people — and how do we maximize that?'

A social media post showcasing user's work + product branding — that's k potentially reaching hundreds of impressions per user.

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Real-world examples

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