What Is Customer Churn? Definition, Formula, and Examples

If you sell a subscription, a membership or any product people buy repeatedly, churn quietly decides how fast you can grow. Acquiring customers fills the bucket; churn is the leak. This guide explains what churn is, the formulas used to measure it, worked examples, and the mistakes that make the numbers misleading.

Why churn matters

Every customer you lose has to be replaced just to stand still. A business can add new customers steadily and still barely grow if churn is high, because the new ones are only covering for the old ones. Tracking churn shows you whether growth is solid or leaky, and it is usually the first number to move when something is wrong with the product, the price or the service.

The customer churn rate formula

The opposite measure is the retention rate:

Example (illustrative numbers). A company starts the month with 500 customers. During the month, 20 of those customers cancel, and 60 new customers join. The churn rate is 20 ÷ 500 = 4%, so retention is 96%. The 60 new customers are not counted in the calculation, because they weren't customers at the start of the month. The company ends the month with 540 customers.

Revenue churn: when customers are not equal

Losing ten small customers is not the same as losing one very large one. Revenue churn measures money rather than headcount.

Example (illustrative numbers). A company starts the month with $50,000 in monthly recurring revenue. Cancellations remove $1,500 and downgrades remove $700, so gross revenue churn is 2,200 ÷ 50,000 = 4.4%. If existing customers also expanded by $1,200 (upgrades or extra seats), net revenue churn is (2,200 − 1,200) ÷ 50,000 = 2.0%. If the expansion had been $3,000 instead, the result would be −1.6%. A negative number, often called negative churn, means existing customers are growing revenue faster than others are leaving.

What counts as "churn" depends on your business

Where there is no cancellation button, you have to choose the window yourself. A business whose customers buy once a year can't call someone churned after 30 quiet days. Whatever you pick, write it down and use it consistently.

Voluntary and involuntary churn

• Voluntary churn: the customer decides to leave, for reasons such as price, a competitor, poor fit, or a bad experience.
• Involuntary churn: the relationship ends without the customer choosing it, usually because of a failed or expired payment method.

They need different fixes. Voluntary churn points to product, service or pricing questions. Involuntary churn is often a billing and communication problem, and can sometimes be recovered with timely reminders and an easy way to update payment details.

Converting monthly churn to annual churn

A common mistake is multiplying the monthly rate by 12. Churn compounds, because each month's loss comes from the customers who remained. With 3% monthly churn, the share still with you after a year is 0.97 raised to the 12th power, about 69.4%, so annual churn is roughly 30.6%, not the 36% you get by multiplying. The formula assumes a steady monthly rate, which real businesses rarely have, so treat it as an approximation.

Common mistakes when measuring churn

• Counting new customers in the starting base. Only customers present at the start of the period belong in the denominator.
• Mixing time periods. Compare monthly with monthly, not monthly with quarterly.
• Relying on one blended number. An average can hide the fact that customers who joined recently leave much faster than long-standing ones. Looking at groups of customers by sign-up month (cohorts) shows this.
• Treating every loss as the same. Separate voluntary from involuntary churn, and customer churn from revenue churn.
• Changing the definition midway. If you redefine churn, your past and present numbers stop being comparable.

From measuring churn to predicting it

Churn rate tells you how many customers you lost. It can't tell you which customers are about to leave. Prediction looks at behavior before the cancellation, such as logins, support history and payment problems, and flags at-risk customers while there is still time to act. Our guide to predicting churn shows how to start.

Frequently asked questions

What is the difference between churn and retention?

They are two sides of the same measure. Churn rate is the share of customers lost over a period, and retention rate is the share kept, so the two add up to 100%.

Is all churn bad?

Not necessarily. Losing customers who were a poor fit, costly to serve, or unlikely to ever succeed with your product can be healthy. The concern is losing the customers you most want to keep, or losing them faster than you can replace them.

How often should I calculate churn?

Monthly is common for subscriptions, but the right interval matches your billing cycle. Calculate it on a consistent schedule and compare like with like.

What is a good churn rate?

It depends on your industry, pricing, and customer type, so there is no single right number. Track your own rate over time, split it by customer group, and judge whether it is improving.