one-line definition
Retention Cohort is a core operating metric that helps small teams make better product and growth decisions.
formula: Group users by signup week, then track the percentage still active at week 1, 2, 4, 8, 12.
tl;dr
A retention cohort groups users by when they signed up, then tracks how many are still active over time. It's the only way to tell whether your product is actually getting better at keeping people.
Simple definition
A Retention Cohort is a group of users who signed up during the same time period (usually a week or month), tracked over subsequent periods to see what percentage remain active. Unlike aggregate churn rate, which blends all users together, cohort analysis isolates each group so you can see if newer users stick around better than older ones.
This distinction matters. Your overall churn rate might be 6% every month, but if your January cohort retains at 45% after 3 months and your March cohort retains at 60%, your product is improving. Aggregate metrics hide this. Cohorts reveal it.
How to calculate it
Group users by signup week, then track the percentage still active at week 1, 2, 4, 8, 12.
Example for a February cohort (100 signups):
| Week | Active users | Retention |
|---|---|---|
| 0 | 100 | 100% |
| 1 | 64 | 64% |
| 2 | 48 | 48% |
| 4 | 35 | 35% |
| 8 | 28 | 28% |
| 12 | 24 | 24% |
The biggest drop is always week 0 to week 1. If you can move that from 64% to 75%, every downstream number improves. That's why onboarding matters so much.
Example
You run a budgeting app. Your November cohort (80 users) has 18% retention at week 8. You redesign the first-run experience in December to show a pre-filled sample budget instead of an empty screen. Your December cohort (90 users) shows 29% retention at week 8. Same product, same marketing channels, but a better first impression. Line up the two cohort curves side by side and you can literally see the impact of that one change. No other metric gives you this clarity on whether a specific product change worked.
Related reading
Related terms
- MRR
- CAC
- LTV
FAQ
Why does Retention Cohort matter?+
It gives a fast signal about whether your product and distribution system is improving or regressing.