What Is Product-Market Fit? How to Tell Whether You Have It
Sean Ellis's 40% test, retention curves, and NPS
They say "you will know when you reach PMF," but it can actually be measured with quantitative metrics. Use indicators like the Sean Ellis test (40% rule), retention curves, and NPS to determine PMF achievement, then establish growth strategies.
Action Steps
1
Measure the percentage of users who would be "very disappointed" without the product using Sean Ellis test
2
Check if weekly/monthly retention curves flatten
3
Monitor if organic growth (word-of-mouth, referrals) occurs
4
If PMF is not achieved, readjust core features or target customers
Pros
- ✓ Growth accelerates after PMF is achieved
- ✓ Marketing efficiency improves dramatically
Cons
- ✗ Requires a long and uncertain period to achieve PMF
- ✗ Market changes can invalidate existing PMF
Use Cases
Product direction review 3-6 months after MVP launch
Preparing PMF proof materials before Series A fundraising