Customer Retention Rate Calculator

Formula

Retention rate = (ending customers − new customers) ÷ starting customers × 100%.

Worked example

With Customers at period start: 1000, Customers at period end: 950, New customers during period: 100, customer retention rate is 85 %.

Inputs and calculation

Remove customers acquired during the measured interval from the final count. The remaining customers are attributed to the original cohort and divided by its starting size. The displayed relationship is Retention rate = (ending customers − new customers) ÷ starting customers × 100%. Keep the fields' displayed units attached when reproducing this relationship by hand.

Worked numerical example

For example, enter customers at period start 1,000, customers at period end 950, new customers during period 100. Those inputs produce customer retention rate of 85 %. The same values also give starting customers retained 850 customers.

Holding the other example values fixed, change customers at period start from 1,000 to 1,001. The main output becomes 84.9151 %. This comparison isolates the effect of that one input.

How to read and use the result

The percentage measures survival of the initial customer group. It is distinct from net customer growth, which can be positive even when many original customers leave. Track cohort stability while separating acquisition from existing-customer behavior.

Practical context

If a business starts with 1,000 customers, ends with 950 and acquired 100 new customers, 850 of the initial group remain and retention is 85%. Looking only at the 950 ending figure would hide a loss of 150 original customers. The definition of an active customer matters: one purchase this month, an open subscription and a login are different events.

Assumptions and scope

Customer identities are deduplicated, new customers are part of the ending count, and period boundaries are consistent. Reactivation and account merging require a documented classification rule. Replace the example defaults with measured inputs for your situation and account separately for factors outside these fields.

Checks and common mistakes

New customers cannot exceed the ending count for this definition. Counting a repeat purchase as a new customer would understate retention.

Common questions

What should I verify before using the Customer Retention Rate Calculator result?

Cohort identifiers and consistent boundaries are necessary before treating the percentage as a trend. A subscription business may measure retention by subscribers, by revenue or by usage. This calculator uses a customer count; it gives the same weight to a tiny account and a large account, so it cannot replace a revenue-retention measure.