Definition
Retention rate is the share of customers who are still active from one period to the next. A 68% retention means a good two-thirds of customers buy again.
Also called: Retention rate, Customer retention, RetentionFollow the same customers over time.
customers buying in month 3. Each column shows the time since acquisition.
01Group customers by the date of their first purchase.
Retention is the lever under acquisition
Retention is the single biggest driver of CLTV: the more customers who stay and buy again, the more an acquired customer is worth, and the more you can afford to pay to win the next one. A brand that keeps 68% versus one that keeps 55% can bid markedly more in the auction and still make money.
That's why retention isn't a soft add-on to performance marketing. It's the half of the equation that decides how aggressively acquisition can be run. Chasing cheap CAC without working on retention is optimizing half the machine.
How retention is built
Retention is built across the whole post-purchase experience: strong onboarding, a product that delivers, relevant post-purchase and replenishment flows, loyalty mechanics and segmented contact that reaches the customer at the right moment. Klaviyo is where much of it is executed.
Measure retention in cohorts, not as one average. An average hides whether newer customers are better or worse than earlier ones — and that trend is exactly what tells you whether your retention is improving or deteriorating.
Frequently asked questions
Why is retention rate more important than many think?
Because it drives CLTV, which sets the ceiling on your allowable CAC. A higher retention makes every acquired customer worth more and lets you bid higher than the competitor — without a single extra ad euro.
How do I best measure retention?
In cohorts: group customers by when they came in, and follow each group over time. That reveals whether retention is improving or deteriorating for newer customers — something an overall average hides.
From insight to action
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About the author
Nicklas Segatz Mortensen
Growth hacker and fractional CMO with 10+ years' experience and hundreds of millions in managed ad spend behind him. Background from larger Danish and international scale-ups, and from the agency world.
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