Churn Rate Calculator
Calculate your churn rate and retention rate from customers lost over a period, plus the implied average customer lifetime.
How to use this tool
- Enter the number of active customers at the start of the period.
- Enter how many of those customers you lost during the period (exclude new signups).
- Read your churn rate, retention rate, customers retained, and implied average lifetime.
Measure how fast you are losing customers. Enter your starting customer count and how many you lost during the period to get your churn rate, retention rate, and the average customer lifetime it implies.
Formula
Churn rate = Customers lost ÷ Customers at start of period × 100%
Retention rate = 100% − Churn rate
Average customer lifetime ≈ 1 ÷ Churn rate (in the same time units as the period)
For a 5% monthly churn rate, the implied average lifetime is 1 ÷ 0.05 = 20 months.
How it works
Churn rate measures the share of customers (or revenue) you lose over a period. The basic customer churn rate divides the number of customers lost during the period by the number you had at the start, then expresses it as a percentage. Its complement is the retention rate. Because the same period unit carries through, a churn rate measured monthly produces a lifetime estimate in months.
This calculator uses the start-of-period denominator, which is the simplest and most common convention. There are nuances it does not model: revenue churn (which weights customers by their spend), net churn (which nets out expansion from existing customers, and can be negative for the best SaaS businesses), and averaging conventions for fast-growing bases. Always exclude new signups from the churned count — churn measures losses among existing customers, not net change. The average-lifetime figure is the standard 1 ÷ churn approximation and assumes a roughly constant churn rate.
Reviewed by the AbraCalc Business Desk. This is an educational estimate, not financial advice; choose the churn definition (customer vs revenue, gross vs net) that matches how your business reports.
Worked example
500 customers, 25 lost in the month
- Churn rate = 25 ÷ 500 = 0.05 = 5.00%.
- Retention rate = 100% − 5% = 95.00%.
- Customers retained = 500 − 25 = 475.
- Average lifetime = 1 ÷ 0.05 = 20.00 periods.
Churn rate = 5.00%, retention rate = 95.00%
Churn rate vs implied average customer lifetime
| Monthly churn | Retention | Avg lifetime (months) |
|---|---|---|
| 1% | 99% | 100.00 |
| 2% | 98% | 50.00 |
| 3% | 97% | 33.33 |
| 5% | 95% | 20.00 |
| 8% | 92% | 12.50 |
| 10% | 90% | 10.00 |
| 20% | 80% | 5.00 |
Key terms
- Churn rate
- The percentage of customers (or revenue) lost over a period.
- Retention rate
- The percentage of customers kept over a period; 100% minus the churn rate.
- Net revenue churn
- Revenue lost from cancellations and downgrades minus revenue gained from expansion; can be negative when expansion outweighs losses.
- Average customer lifetime
- Roughly the reciprocal of the churn rate; how many periods an average customer stays before churning.
Frequently asked questions
- What is a good churn rate?
- It depends heavily on segment. Many established SaaS businesses target monthly customer churn under 1–2%; small-business and consumer products often run higher. Lower is better, and the best companies achieve negative net revenue churn through expansion.
- Should I exclude new customers from the calculation?
- Yes. Churn measures losses among customers who already existed at the start of the period. Including new signups in the lost-customer count, or in the denominator mid-period, distorts the rate. Use the start-of-period base.
- How does churn relate to customer lifetime?
- Average lifetime is approximately 1 divided by the churn rate, in the same time units. A 5% monthly churn implies an average lifetime of about 20 months. This approximation assumes churn stays roughly constant over time.