Churn Rate
The percentage of customers or revenue lost in a period.
Churn measures what you lose. Customer churn counts departing customers; revenue churn counts the revenue they took with them. The two differ when small and large customers behave differently.
Monthly churn compounds harshly. 5% monthly is roughly 46% annually — nearly half the customer base replaced each year just to stay flat.
For early-stage SaaS, under 3% monthly logo churn is generally acceptable and under 1% is strong. Enterprise businesses are held to lower numbers because contracts are longer and the sales cost is higher.