Formula
Customers lost in period / Customers at start of period x 100
How to measure
Divide the count of customers who churned during a month by the total customer count at the start of that month.
Why track it
Churn rate directly caps growth; a company adding 5% new customers a month while churning 5% is standing still.
Example
A company with 1,000 customers at the start of the month loses 40, a monthly churn rate of 4%.