Churn rate is the percentage of customers who stop buying from you during a period. If you start January with 500 subscribers and 15 cancel during the month, monthly customer churn is 3%. Revenue churn does the same sum with money rather than headcount, which matters when your customers are different sizes.
Churn is the number that tells a growing business whether it is filling a bucket or a sieve. A gym chain signing 200 new members a month sounds healthy until you learn 180 are leaving. A software company with 5% monthly churn loses roughly half its customers every year and has to replace them before it can grow at all. Churn also tends to move before revenue does, which makes it an early warning.
Two common confusions. First, churn should count customers who could have left, so exclude those who joined mid-period from the starting base. Second, decide whether a downgrade is churn: for revenue churn it is partly; for customer churn it is not. Write the definition down and stick to it, because a churn rate that changes definition every quarter cannot be trended.
In Klayara, churn is a calculated field defined once from your billing or CRM data, then trended, broken down by plan or region, and watched on the customer health or SaaS metrics template.