Hong Life CalculatorsUnderstanding the customer churn rate calculator — concept and principle
Churn rate is the share of customers who stop doing business with you during a period. Subscription businesses, SaaS companies, telecoms, gyms and membership services track it every month, because even a small monthly churn compounds into a large yearly loss. This calculator turns one month's figures into monthly churn, compounded annual churn and the implied average customer lifetime.
How it is calculated
Monthly churn = customers lost ÷ customers at start × 100
Annual churn = (1 − (1 − monthly churn)^12) × 100
Average customer lifetime (months) = customers at start ÷ customers lost = 1 ÷ monthly churn
- Customers at start: active customers on the first day of the month.
- Customers lost: customers from that starting group who cancelled or lapsed during the month. New sign-ups are not counted.
The principle
Annual churn is not 12 × monthly churn. Each month you lose a share of the customers who are still left, not of the original group, so survival multiplies: after 12 months, (1 − 0.045)^12 of the starting customers remain. One minus that is the annual churn. Customer lifetime follows from the same constant-rate assumption: if each customer has a 4.5% chance of leaving each month, the expected number of months before leaving is 1 ÷ 0.045 (the mean of a geometric distribution).
Worked example
- Monthly churn: 90 ÷ 2,000 × 100 = 4.5%.
- Retained after one month: 1 − 0.045 = 0.955.
- Retained after 12 months: 0.955^12 ≈ 0.5755.
- Annual churn: (1 − 0.5755) × 100 = 42.45%.
- Average lifetime: 2,000 ÷ 90 ≈ 22.2 months.
How to read the result
Lower is better, but what is "good" depends on the market. Consumer subscriptions often churn several percent a month, while contracts sold to businesses usually churn far less. The lifetime figure feeds customer lifetime value (LTV ≈ monthly margin per customer × lifetime). Note how sensitive it is: cutting monthly churn from 4.5% to 3% raises the lifetime from about 22 to about 33 months.
Common mistakes
- Including customers who joined during the month in the "lost" count or the starting base.
- Multiplying monthly churn by 12 instead of compounding.
- Treating the lifetime as exact when churn is usually higher for new customers and lower for loyal ones.
Frequently asked questions
What is the difference between churn and retention?
Over the same period, retention = 100% − churn for the starting group. Retention looks at who stayed, churn at who left.
Should I calculate churn monthly or annually?
Use the period that matches your billing. Monthly plans are best tracked monthly; annual contracts are better measured at renewal.
What is net revenue churn?
Revenue lost from cancellations and downgrades minus extra revenue from upgrades of existing customers. It can be negative when expansion outweighs losses.
Sources: Farris, Bendle, Pfeifer & Reibstein, Marketing Metrics (Pearson) — retention, churn and customer lifetime value · Gupta, S. & Lehmann, D. R., Managing Customers as Investments (Wharton School Publishing)