Calculate Customer Churn Rate
What This Tool Is
Churn Rate Calculator is a customer retention analysis tool that converts lost-customer counts into churn and retention percentages.
It also converts monthly and yearly churn to comparable values and estimates customer lifespan from your churn rate.
Quick Answer
Customer churn rate is the percentage of customers you lose in a period. The core formula is:
churn rate = (lost customers / customers at start) x 100
Retention rate for the same period is:
retention rate = 100 - churn rate
How the Churn Math Works
| Metric | Formula | Use |
|---|---|---|
| Period churn | lost / start |
Raw churn for your selected period |
| Retention | 1 - period churn |
Share of customers kept in same period |
| Annualized churn | 1 - (1 - monthly churn)^12 |
Compare monthly churn on a yearly basis |
| Average lifespan | 1 / monthly churn |
Approximate months a customer stays |
| Half-life | ln(0.5) / ln(1 - monthly churn) |
Months until half your customers remain |
Inputs and Outputs
| Field | What you enter | What you get |
|---|---|---|
| Customers at start | Total active customers at period start | Baseline for churn denominator |
| Customers lost | Customers who canceled or churned in period | Numerator for churn calculation |
| Period | Month or year | Correct churn interpretation and conversion |
| Results | Calculated automatically | Churn, retention, annualized churn, lifespan, half-life |
Worked Examples
| Scenario | Inputs | Result |
|---|---|---|
| Monthly SaaS cohort | Start 1200, Lost 48, Period month | Monthly churn 4.00%, retention 96.00%, annualized churn 38.73% |
| Yearly contract base | Start 5000, Lost 600, Period year | Yearly churn 12.00%, monthly equivalent churn about 1.06% |
| Edge case | Start 900, Lost 0, Period month | Churn 0.00%, retention 100.00%, lifespan and half-life shown as infinity |
Common Mistakes
- Mixing new customers into the starting customer count for the same period.
- Comparing monthly churn directly against yearly churn without conversion.
- Using lost customers greater than starting customers, which is inconsistent input.
- Treating one abnormal month as a long-term trend without checking multiple periods.
FAQ
What is customer churn rate?
Customer churn rate is the percentage of customers lost during a period. It is calculated as lost customers divided by customers at the start of the period.
How is retention rate related to churn?
Retention and churn are complements for the same period. If churn is 4%, retention is 96%.
Why does this calculator show annualized churn?
Annualized churn makes monthly churn easier to interpret for yearly planning. It applies compounding rather than simply multiplying by 12.
What does average customer lifespan mean?
It is an estimate of how many months a customer stays, based on your monthly churn. It is a planning estimate, not a guarantee for each customer.
Can churn be above 100%?
For a single period with consistent counting, no. This page blocks results when lost customers exceed starting customers.
Does this include revenue churn?
No. This calculator focuses on customer count churn, not MRR or revenue churn.
Is this churn calculator private?
Yes. Calculations run in your browser and no login is required.
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Privacy and Limits
This tool runs entirely in your browser for calculation. It does not generate invoices or financial statements.
Use verified source data from your analytics or billing systems before making reporting or budget decisions.
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