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Viral Coefficient Calculator

Calculate your product's viral growth potential and K-factor

Viral Metrics
Enter your user growth and referral data

How many people does each user invite?

% of invites that become active users

Time between user signup and sending invites

Formula Explained

Viral Coefficient (K)

K = Invites per User × Conversion Rate

Interpretation

  • K > 1: Viral growth (exponential)
  • K = 1: Flat growth (sustainable)
  • K < 1: Declining (needs paid acquisition)
Viral Coefficient (K-Factor)
Your product's viral growth metric

Your K-Factor

0.75

⚠️ Not Viral Yet

You need paid acquisition or better referral mechanics

Growth Rate per Cycle+75.0%
Cycle Time7 days
Growth Projections
Current Users1.0K
After 1 Cycle (7 days)1.8K
After 5 Cycles (35 days)16.4K
After 10 Cycles (70 days)269.4K
Understanding Viral Growth

What is Viral Coefficient?

The viral coefficient (K-factor) measures how many new users each existing user brings to your product through referrals. It's the key metric for understanding viral growth potential.

Improving Your K-Factor

Increase Invites Sent

  • • Make sharing easy and visible
  • • Incentivize referrals
  • • Add social features

Improve Conversion Rate

  • • Optimize landing pages
  • • Reduce signup friction
  • • Show social proof

Reduce Cycle Time

  • • Prompt sharing early
  • • Create "aha moments" faster
  • • Automate invitations

Network Effects

  • • Make product better with friends
  • • Build in collaboration
  • • Create FOMO

Real-World Examples

  • Dropbox: K ≈ 0.15-0.35 (referral program with storage incentives)
  • PayPal: K ≈ 1.0+ early days ($10 referral bonus drove virality)
  • Hotmail: K ≈ 1.5+ ("PS: I love you" signature)
  • Instagram: K ≈ 1.0+ (easy photo sharing to other networks)

Important Considerations

  • K-factor alone doesn't guarantee success - retention matters too
  • Viral growth compounds - small improvements have massive long-term impact
  • Most products start with K < 1 and improve through iteration
  • Even K = 0.5-0.7 significantly reduces customer acquisition costs
  • Sustainable K > 1 is rare - requires exceptional product-market fit