Customer Churn Calculator
The Leak That's Easy to Ignore Until It Isn't
Growth from new customers can mask a business quietly losing its existing ones. Churn rate names that leak directly: the share of customers who were around at the start of a period and simply weren't there by the end. It's an uncomfortable number for a reason — it's usually the clearest early signal that something in the product, pricing, or service experience needs attention.
Where This Calculation Gets Used
- Subscription and SaaS health checks — monthly or annual churn is one of the first metrics investors and boards ask about.
- Comparing cohorts — tracking churn separately for different signup periods or plan tiers to spot which segment is unstable.
- Justifying retention spend — a high churn rate builds the case for investing in onboarding, support, or loyalty programs rather than only acquisition.
- Reconciling with revenue — customer churn paired with revenue churn shows whether the customers leaving were high-value or low-value.
The Formula
Retention Rate = 100% − Churn Rate
Worked Examples
| Customers at Start | Customers Lost | Churn Rate | Retention Rate |
|---|---|---|---|
| 2,000 | 140 | 7.0% | 93.0% |
| 500 | 25 | 5.0% | 95.0% |
| 10,000 | 850 | 8.5% | 91.5% |
Churn compounds over time: a steady 5% monthly churn rate loses far more than 5% of a customer base across a full year, since each month's losses come out of an already-shrunk base.
How to Use This Calculator
- Enter Customers at Start of Period — the customer count at the beginning of the period you're measuring.
- Enter Customers Lost During Period — how many of those customers churned out by the end.
- Select Calculate to get both the churn rate and the corresponding retention rate.
Related Calculations
For a retention rate that also accounts for new customers gained during the period, use the Customer Retention Calculator. To see how churn affects long-run customer value, check the Customer Lifetime Value Calculator.