How many new users each user brings. The Viral Coefficient (K-Factor) Calculator takes invitations sent per user, invitation conversion rate and returns viral coefficient (k) plus reading, users after one cycle from 100 seed users. Results update as you type, and the formula is shown under the result so you can repeat it in your own spreadsheet.
Marketing metrics are most useful as trends and comparisons between channels. Measure every campaign the same way, over the same period, and judge it against your gross margin rather than against revenue alone. Use the worked example below to check the maths against your own figures.
How the Viral Coefficient (K-Factor) Calculator works
A coefficient above 1 means each user brings more than one new user and growth compounds on its own. Most products live below 1, where referrals amplify paid growth rather than replace it.
Worked example
With the example values (invitations sent per user of 5, invitation conversion rate of 12%), the viral coefficient (k) is 0.6; reading Sub-viral: growth still needs other channels, users after one cycle from 100 seed users 160. Change any figure above and the result updates immediately; use Copy results to paste the summary into a note or email.
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Frequently Asked Questions
How is viral coefficient (k) calculated?
K = invitations per user × conversion rate of an invitation.
Which figures do I need?
Invitations sent per user, invitation conversion rate. Take them from the same period and the same set of accounts or reports so the ratio is consistent, and check the example values as a guide to the units expected.
How often should I track this metric?
Weekly for live campaigns, monthly for channel comparisons, and always over the same period for spend and results so the figures line up.
