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About this tool
Customer churn and retention rate for a period.
The Churn Rate Calculator divides the customers you lost during a period by the customers you had at the start of it, giving customer churn as a percentage along with the matching retention rate and the headcount left. It is for subscription and SaaS teams, membership operators and account managers who need one defensible number for a monthly or quarterly review. Retention is reported as 100% minus churn, and remaining customers as start minus lost, so every figure on screen traces back to the two numbers you entered.
Open Churn Rate Calculator on AltFTool — it loads instantly in your browser.
Enter the number of customers your business had at the start of the period you're analyzing into the 'Customers at start' field of the Churn Rate Calculator.
Input the number of customers your business lost during that same period into the 'Customers lost' field.
There is no Calculate button - the Result panel recomputes as you type, showing '5.00% churn' for the 1000 and 50 defaults, with Retention rate and Customers remaining listed beneath it.
Retention is derived as 100% minus churn on the identical denominator, so the two numbers can never disagree with each other.
Alongside the percentages it returns customers remaining, which is the figure you actually forecast next period's revenue from.
Churn is reported to 0.01%, enough resolution to see a move from 4.90% to 5.10% that a rounded whole-number dashboard would hide.
Churn rate = customers lost during the period ÷ customers at the start of the period × 100. Losing 50 of 1,000 starting customers is 5.00% churn, leaving 950 customers and a 95.00% retention rate.
No — this is the standard simple churn formula, which measures losses only against the opening customer count. New signups are deliberately excluded from the denominator so that fast growth cannot mask a rising cancellation rate.
Compound it rather than multiplying by 12. Monthly churn of 5% means 95% survive each month, so annual retention is 0.95¹² ≈ 54%, implying about 46% of the starting cohort is gone after a year — not 60%.
Customer churn — it counts accounts, not money. If your customers pay very different amounts, run the same formula on revenue instead by entering starting recurring revenue and revenue lost, which gives gross revenue churn.
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