Question 1

What is a viral loop?

Accepted Answer

A viral loop is a mechanism built into a product that causes users to naturally expose it to new people as part of normal usage. Unlike traditional referral programs, viral loops are native to the product experience — users share because they need to, not because they're asked to.

Question 2

What is k-factor in viral growth?

Accepted Answer

K-factor (viral coefficient) measures how many new users each existing user brings. It's calculated as: k = invites per user x conversion rate. A k-factor above 1 means exponential growth — each user brings more than one new user.

Question 3

What is a good k-factor for a SaaS product?

Accepted Answer

Most SaaS products have a k-factor between 0.1 and 0.5. A k-factor of 0.3 means every 100 users from paid channels generate 43 additional users for free. A k-factor above 0.7 is excellent, and above 1.0 means self-sustaining viral growth.

Question 4

What is viral cycle time?

Accepted Answer

Viral cycle time is the average number of days between when a user joins and when they invite or expose others to the product. Shorter cycle times accelerate growth exponentially. The best viral loops have cycle times under 7 days.

Question 5

How is a viral loop different from a referral program?

Accepted Answer

A referral program asks users to share in exchange for rewards. A viral loop makes sharing a natural part of using the product. Calendly users share links because they need to book meetings, not because they get a discount. Viral loops are more sustainable and have higher conversion rates than incentivized referrals.

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