Practical guide
Customer churn rate formula: use the starting customer base
Calculate customer churn with an example and avoid including newly acquired customers in the denominator.
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How is customer churn rate calculated?
Divide customers lost during a reporting period by customers present at the start, then multiply by 100. Use a consistent definition of a lost customer and keep the period visible next to the percentage.
A monthly churn example
An illustrative business starts the month with 800 customers and loses 24 from that starting base. Monthly customer churn is 24 ÷ 800 × 100 = 3%. If it also acquires 80 customers, it ends with 856, but those new customers do not increase the starting denominator.
Entering 856 instead of 800 produces about 2.80%. That makes churn appear lower solely because the denominator changed. In the calculator, enter the starting 800 and the lost 24 to preserve the cohort basis.
Reconcile customer movement
Write a simple bridge: 800 opening customers + 80 new customers − 24 lost customers = 856 ending customers. If the actual ending count differs, investigate reactivations, duplicate accounts, mergers, or changes to the paid-customer definition.
For customers acquired and lost within the same period, document a separate treatment rather than silently counting them against a starting cohort they never belonged to. The calculator accepts only two counts and cannot enforce that reporting policy for you.
Churn questions
Is customer churn the same as revenue churn?
No. Losing one large customer and one small customer has the same effect on a customer count but can have very different revenue effects. This tool does not weight losses by contract size.
Is retention always 100% minus churn?
For the same starting cohort and a simple retained-versus-lost definition, yes: 3% lost leaves 97% retained. Mixing new customers or reactivations into the retention calculation changes the comparison.
Can the output exceed 100%?
The raw ratio can if the entered lost count exceeds the starting count. That indicates inconsistent inputs for this cohort definition. Correct the counts rather than interpreting the output as a valid retention measure.
Use the churn rate calculator to reproduce the scenario with your own inputs.