Customer Retention Rate
Customer retention rate is the percentage of a starting customer population that remains active under a stated rule at a later point or period.
What is Customer Retention Rate?
Retention follows a defined population through time. New customers acquired after the starting point do not belong in the retained count for that original group. In ecommerce, “active” might mean an ongoing subscription or a qualifying purchase during a later interval.
Without a subscription contract, a customer does not explicitly announce that the relationship has ended. A purchase-based retention rule therefore describes observed activity, not a permanent verdict about loyalty. State the qualifying behavior and time window.
Retention rate (%) = Starting customers meeting the later activity rule ÷ Starting customers × 100
The common (ending customers − new customers) ÷ starting customers shortcut only works when those counts identify the retained starting population consistently.
Tracking an existing subscription base
A pet-food subscription starts the month with 300 active customers. At month-end, 270 of those original customers remain active. Retention is 90%. Forty newly acquired subscribers bring the total active base to 310, but they do not improve the original group’s retention percentage.
How to interpret it
Retention separates keeping existing relationships from acquiring new ones. A growing total customer count can conceal poor retention if a large inflow of new customers replaces those who leave. Follow the original group directly when possible.
The activity rule determines the meaning. A customer who ordered last quarter but not this quarter may fail a quarterly repurchase rule while still being a future buyer. A subscription cancellation provides a more explicit ending event.
Retention can be measured at a specific interval or across a cumulative window. “Purchased in month three” differs from “purchased at least once by month three.” Label that difference before comparing reports or cohorts.
Retained customers can still become less profitable if discounts, service costs or returns increase. Customer-count retention does not show the revenue or contribution retained from the group. Those are separate economic views.
Common mistakes
Including new customers as retained customers
New acquisition belongs to growth reporting. Retention keeps the starting population fixed.
Assuming retention always equals repeat purchase rate
Repeat purchase rate asks whether customers bought again under its window. Retention asks whether a starting population meets a later activity rule. They coincide only under matching definitions.