Churn rate is the share of customers, or of recurring revenue, lost over a period: what was lost from the starting base divided by the starting base. Where there is no subscription, a customer is lost when silence exceeds a stated multiple of its own order cadence, and churned revenue is the run rate before the silence.
Churn rate means the percentage of the customers, or of the recurring revenue, a business had at the start of a period that it lost during the period. Customer churn counts accounts; revenue churn weighs them by what they paid.
On the same basis, they sum to 100 percent. Renewal rate does not, because its denominator is only what was due.
A lost customer that returns is a reactivation in the period it returns. Last year's churn is not rewritten.
Churn rate % = customers lost in the period ÷ customers at the start of the period × 100. Revenue churn uses recurring revenue lost ÷ recurring revenue at the start. New customers won in the period are left out of both. Where there is no contract to cancel, lost is defined by a stated rule on silence.
A base of 400 customers and $12.0 million at the start of the year lost 36 customers worth $0.6 million: 36 ÷ 400 = 9 percent by count and $0.6 million ÷ $12.0 million = 5 percent by revenue.
Quoted by count only, or with new customers netted off. Churn is about what was lost from the starting base; growth is a separate line.
For how churn sits beside renewal and retention rates, see renewal rate, retention rate and churn rate; without a subscription, see B2B churn without a subscription.