Free tool
Cohort Retention Calculator
Put each week's signups on one line and enter how many came back in each following week to get a retention table. Everything is calculated in your browser.
Write "signups, week 1, week 2, …" on each line, separated by commas or spaces. Leave weeks that haven't ended empty. Up to 12 lines and 12 weeks.
| Cohort | Signups | Week 1 | Week 2 | Week 3 | Week 4 |
|---|---|---|---|---|---|
| 1 | 120 | 50.0% | 35.0% | 25.0% | 22.5% |
| 2 | 95 | 53.7% | 42.1% | 34.7% | |
| 3 | 80 | 55.0% | 38.8% | ||
| 4 | 64 | 46.9% | |||
| Average | 51.5% | 38.3% | 29.3% | 22.5% |
Averages only include cohorts that have finished that week. Counting unfinished cohorts as zero makes recent weeks look worse than they are.
Cells with fewer than 30 people in the denominator show counts (returned/signups) instead of a rate.
What is cohort retention?
It shows how many people who signed up in the same period (a cohort) came back in each later week. If 120 people signed up in a week and 60 came back in week 1, week-1 retention is 50%. Because cohorts aren't mixed, it is a good way to compare before and after a product change.
Leave unfinished weeks blank
A cohort that signed up yesterday hasn't reached week 2. Entering zero there drags the average down and makes retention look worse. This calculator only adds up cohorts that have a value for that week.
Read small cohorts as counts
30% retention in a week with 10 signups is three people. One person moves it by 10 points, so below 30 people the count is a more honest reading than the rate.
Frequently asked questions
What counts as "coming back"?
It's up to you, but keep one rule for the whole table - for example, signed in that week, or used the key feature that week - and count every cell the same way.
Can I use days or months instead of weeks?
Yes. The calculator only sees numbers, so read the columns as days or months and the math is the same. Only the column headers say weeks.
Is the average a simple average?
No, it's weighted by people. Returning users across cohorts are added up and divided by the summed signups, so larger cohorts carry more weight.
Are my numbers stored?
No. The calculation runs in your browser. The number grid is kept in the address so you can reopen it, so don't share the link if the numbers are private.
Compare retention across products with one rule, in one table
funnellog isn't for sale. It's an operator-only tool that compares every product's funnel with the same rules.