Churn is the rate at which subscription customers cancel or downgrade in a given period. Gross churn counts only departures; net churn subtracts expansion from the same cohort.
Healthy B2B SaaS typically sees 0.5-1.5% monthly gross churn. SMB SaaS runs 2-5%. Anything north of 5% signals product-market-fit or pricing issues that compound into revenue death spirals if not addressed.