# What is my churn rate?

Computes the customer churn rate for a period (customers lost ÷ customers at the start × 100) and the retention rate, from customers at the start, at the end and new, or from the customers lost.

- Page: https://www.acalculator.org/finance/churn-rate-calculator
- JSON spec: https://www.acalculator.org/finance/churn-rate-calculator.json
- Version: c6c1d7752ca4

## Default answer

Example with the default inputs (I know the Start, end and new, Customers at the start 400, Customers at the end 410, New customers 30): 20 lost out of 400 at the start is a churn rate of 5% and a retention rate of 95%.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| from | I know the | Whether you know the customers at the start, at the end and new, or the customers lost. |
| start | Customers at the start | Customers you had at the start of the period. |
| end | Customers at the end | Customers you had at the end of the period. |
| new | New customers | Customers you gained during the period. |
| lost | Customers lost | Customers from the start of the period who left during it. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| churn | Churn rate | Customers lost ÷ customers at the start × 100. |
| retention | Retention rate | (Customers at the end − new customers) ÷ customers at the start × 100, which is 100 − churn rate. |
| customersLost | Customers lost | Customers at the start − customers kept. |
| kept | Customers kept | Customers from the start who are still customers at the end. |

## Method

Customers kept = customers at the end − new customers (or customers at the start − customers lost); churn rate = customers lost ÷ customers at the start × 100; retention rate = customers kept ÷ customers at the start × 100.

## Assumptions

- The customers lost are customers from the start of the period; new customers gained during the period are all still customers at its end.
- Arithmetic is exact on the typed counts; the rates show to 2 decimals.

## Worked examples

1. from = counts, start = 400, end = 380, new = 0 gives churn = 5%, retention = 95%, customersLost = 20, kept = 380. Source: HubSpot, "Customer Churn — What It Is And Why It Matters for Every Business" (churn rate = customers lost in the period ÷ customers at the start; 400 at the start and 380 at the end is 20 ÷ 400 = 5%). https://blog.hubspot.com/service/what-is-customer-churn; HubSpot, "7 Ways to Boost Your Customer Retention Rate" (retention rate = (customers at the end − new customers) ÷ customers at the start × 100%). https://blog.hubspot.com/service/customer-retention-rate: (380 − 0) ÷ 400 × 100 = 95.
2. from = counts, start = 400, end = 410, new = 30 gives churn = 5%, retention = 95%, customersLost = 20. Source: HubSpot, "7 Ways to Boost Your Customer Retention Rate" (retention rate = (customers at the end − new customers) ÷ customers at the start × 100%). https://blog.hubspot.com/service/customer-retention-rate.
3. from = lost, start = 1,250, lost = 75 gives churn = 6%, retention = 94%, kept = 1,175. Source: HubSpot, "Customer Churn — What It Is And Why It Matters for Every Business" (churn rate = customers lost in the period ÷ customers at the start; 400 at the start and 380 at the end is 20 ÷ 400 = 5%). https://blog.hubspot.com/service/what-is-customer-churn.
4. from = lost, start = 3, lost = 1 gives churn = 33.333333%, retention = 66.666667%. Source: HubSpot, "Customer Churn — What It Is And Why It Matters for Every Business" (churn rate = customers lost in the period ÷ customers at the start; 400 at the start and 380 at the end is 20 ÷ 400 = 5%). https://blog.hubspot.com/service/what-is-customer-churn.

## FAQ

### What is the churn rate?

The churn rate is the share of your customers who stopped being customers during a period, such as a month or a quarter. It is written as a percent of the customers you had at the start of the period.

### How do I calculate the churn rate?

Divide the customers you lost during the period by the customers you had at the start, and multiply by 100. Starting a quarter with 400 customers and ending with 380, with no new ones, means 20 were lost: 20 ÷ 400 × 100 = 5%.

### How do I calculate the retention rate?

Take the customers at the end of the period, subtract the new customers you gained during it, divide by the customers at the start, and multiply by 100. With 400 at the start, 410 at the end and 30 new: (410 − 30) ÷ 400 × 100 = 95%.

### How are churn and retention related?

They add up to 100%. Every customer you had at the start either stayed (retention) or left (churn), so a 5% churn rate means a 95% retention rate.

### Why subtract new customers?

New customers were not there at the start, so they cannot be part of the churn or the retention of that group. Counting them would make the customers you lost look fewer than they are.

### What if some new customers also left during the period?

These formulas follow only the customers you had at the start, and assume every new customer is still there at the end. If new customers also left, count only the customers from the start of the period who left, and use the Customers lost option.

## Sources

- HubSpot, "Customer Churn — What It Is And Why It Matters for Every Business": churn rate = customers lost during the period ÷ customers at the start of it; 400 at the start and 380 at the end is 20 ÷ 400 = 5%. https://blog.hubspot.com/service/what-is-customer-churn (retrieved 2026-10-18)
- HubSpot, "7 Ways to Boost Your Customer Retention Rate": retention rate = (customers at the end − new customers acquired during the period) ÷ customers at the start × 100%. https://blog.hubspot.com/service/customer-retention-rate (retrieved 2026-10-18)