PMF Is Not a Feeling — It's Measurable
Product-market fit is when your product meets a market's needs so well that it sells itself, retains users, and generates word-of-mouth. The mistake founders make is treating PMF as a vague feeling of momentum. It's actually measurable, and you need to measure it before you scale.
The Sean Ellis Test
Survey users who've experienced your core value: "How would you feel if you could no longer use [Product]?" If 40%+ say "Very disappointed" — you have PMF. Below 40%: you don't. This simple test, run on users who've had at least one meaningful interaction with your product, is the most reliable early PMF signal.
Retention Curves: The Best PMF Signal
Plot weekly/monthly retention cohorts. If your retention curve flattens (even at 20–30%), you have a retained user base to grow from. If it slopes to zero, every cohort churns out. No retention = no PMF. For B2B SaaS, good PMF signals: month-12 retention above 70%, NPS above 40, expansion revenue (users upgrading).
Qualitative PMF Signals
Users call you when the product is down. Users refer colleagues without being asked. Users integrate your tool into critical workflows. Users complain about missing features (not having) vs. canceling. Inbound inquiries exceed your outbound efforts.
What to Do Before PMF
- Talk to users weekly. Not surveys — actual calls.
- Ship features based on patterns in churn conversations, not feature requests
- Cut features that nobody uses (simplify)
- Narrow your ICP to the cohort with highest retention
- Do not scale marketing until retention curve flattens