Quick answer
Churn rate = customers lost ÷ customers at the start of the period × 100. Losing 50 of 1,000 customers is a 5% churn rate and a 95% retention rate.
Enter the customers lost and the customers at the start. The calculator returns churn and retention.
Related tools: Retention Rate Calculator: Customer retention over a period. Net Revenue Retention Calculator: Net and gross revenue retention for a starting recurring-revenue base. Conversion Rate Calculator: Share of visitors who convert.
How to use the Churn Rate Calculator
- Enter customers lost (0 or more).
- Enter customers at start (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Customers lost | A number | ≥ 0 |
| Customers at start | A number | > 0 |
Formula and method
Formula
churn = customers lost ÷ customers at start × 100
IEEE-754 double precision; shown to the decimals indicated.
New customers added during the period are excluded.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Customers lost = 50; Customers at start = 1000.
| Result | Value |
|---|---|
| Churn rate | 5% |
| Retention rate | 95% |
Example 2
Inputs: Customers lost = 3; Customers at start = 120.
| Result | Value |
|---|---|
| Churn rate | 2.5% |
| Retention rate | 97.5% |
Example 3
Inputs: Customers lost = 0; Customers at start = 80.
| Result | Value |
|---|---|
| Churn rate | 0% |
| Retention rate | 100% |
The first line is the headline result (churn rate). Below it the churn Rate Calculator lists retention rate, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Monthly versus annual churn
5% a month sounds small but compounds: retention of 0.95^12 = 54%, so almost half of customers are gone within a year. Always state the period. Annual churn is about 1 − (1 − monthly churn)^12, not 12 times the monthly figure.
Count only the starting group
Customers who joined during the period should not be in the denominator or the lost count, or churn will look lower than it is. Revenue churn weights customers by what they pay and can differ from customer churn.
How the result changes with customers lost
Holding every other input at the first worked example, this table changes only customers lost. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Customers lost | Churn rate | Retention rate |
|---|---|---|
| 25 | 2.5% | 97.5% |
| 50 | 5% | 95% |
| 100 | 10% | 90% |
| 200 | 20% | 80% |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Customers at start: entering "0" shows "Customers at start must be greater than 0." beside that field and no result.
- Customers lost: entering "50" shows "Lost customers cannot exceed the starting number." beside that field and no result.
Choosing between the Churn Rate Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Retention Rate Calculator](/business/retention-rate-calculator/) | customers at start, customers at end and new customers acquired | Retention rate |
| [Net Revenue Retention Calculator](/business/nrr/) | starting recurring revenue, expansion revenue and contraction revenue | Net revenue retention |
| [Conversion Rate Calculator](/business/conversion-rate-calculator/) | conversions and visitors | Conversion rate |
| [Productivity Rate Calculator](/business/productivity-rate-calculator/) | output and input | Productivity |
| [Utilization Rate Calculator](/business/utilization-rate-calculator/) | billable hours and available hours | Utilization rate |
Background: business metrics
Business ratios depend on exactly which costs and revenues you include, so read each page's definition. Two common checks: break-even units = fixed costs ÷ (price − variable cost per unit), so $50,000 of fixed costs with a $10 price and $5 variable cost breaks even at 10,000 units; and net profit margin = net profit ÷ revenue, so $20,000 profit on $100,000 revenue is 20%.
Return on investment ignores time: 20% over five years is far less impressive than 20% in one, so compare returns over the same period.
Assumptions and limitations
- Lost cannot exceed start
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for customers at start and customers lost to confirm this.
Frequently asked questions
What is a good churn rate?
For subscriptions, monthly churn of 1 to 5% is common, depending on the market.
How does churn relate to lifetime value?
Expected lifetime is 1 divided by churn.
Is churn the opposite of retention?
Yes, they add to 100%.
What does the Churn Rate Calculator calculate?
Share of customers lost over a period. It returns Churn rate and Retention rate.
What formula does the Churn Rate Calculator use?
churn = customers lost ÷ customers at start × 100. New customers added during the period are excluded.
What do I need to enter in the churn Rate Calculator?
You enter Customers lost and Customers at start.
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Lost cannot exceed start.
What is an example of a churn Rate result?
With customers lost 50 and customers at start 1000, the churn rate is 5%.
Related calculators
- Retention Rate Calculator — Customer retention over a period.
- Net Revenue Retention Calculator — Net and gross revenue retention for a starting recurring-revenue base.
- Conversion Rate Calculator — Share of visitors who convert.
- Productivity Rate Calculator — Productivity from output and input (hours, workers or cost).
- Utilization Rate Calculator — Billable hours as a share of available hours.
Sources
- Common definition used on this page. No single authoritative standard defines it, so the exact formula is stated in the formula section above
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.