Plain definition
Customer retention is the share of customers from a starting cohort who remain active at the end of a stated period. It is the complement of customer churn when the definitions and cohort match. New customers must be excluded from the numerator, otherwise sales growth can make retention look stronger than it is.
Retention measures relationship continuity, not revenue quality. A retained customer may reduce its spend, while a customer that leaves may have been very small. Read it with revenue retention and cohort age.
Illustrative example
Suppose 200 customers are active at the start of a quarter and 188 of those same customers remain active at the end. Customer retention is 94%. The 30 customers acquired during the quarter are useful for growth reporting but do not enter this calculation.
If retention is weaker among customers acquired through one channel, management should review promise-setting, onboarding, and early product use for that cohort.
| Starting customers retained at period end | |
|---|---|
| Starting customers | |
| Convert to percentage | |
| Customer retention |
Define active consistently and do not count a paused or unpaid account as retained without an explicit policy.
Why it matters
Retention shows whether acquisition creates durable relationships. A high volume of new customers cannot indefinitely compensate for a weak starting cohort.
Practical consequence
Freeze the starting cohort and record active status at the end date. Report retention by acquisition month, segment, plan, and tenure; compare customer and revenue retention. Use the patterns to choose an intervention and measure it against a later matched cohort.