You have product-market fit when users are pulling the product from you faster than you can push it to them. The clearest signal is organic growth: users signing up without paid acquisition, referring others, and complaining when the product is down. If you have to convince people to use your product, you do not have PMF yet.
Quantitative Signals
The Sean Ellis test. Survey active users: "How would you feel if you could no longer use [product]?" If 40%+ say "very disappointed," you have product-market fit. Below 40%, keep iterating.
Use the PMF Calculator to run this survey analysis and benchmark your score.
Retention curves. Plot your Day 1, Day 7, Day 30, and Day 90 retention. If the curve flattens (stops declining) at any point above 20%, you have a retained cohort that finds ongoing value. If it declines to near-zero, you have a leaky bucket.
Organic growth rate. Track what percentage of new signups come from organic channels (word of mouth, direct traffic, organic search). Pre-PMF, this is typically under 20%. Post-PMF, it climbs above 40%.
Revenue retention. Net revenue retention above 100% means existing customers are expanding faster than they churn. This is the strongest financial signal of PMF. Monitor this with the NRR calculator.
The Process
Finding PMF is not a single moment. It is a series of iterations:
1. Pick a narrow segment. Do not try to serve everyone. Find 10 users who have the problem you are solving and talk to them weekly. The user persona builder can help you define this segment precisely.
2. Solve one problem completely. Build the minimum solution that makes those 10 users say "I cannot go back to the old way." This is not an MVP with half-built features. It is a focused product that does one thing exceptionally well.
3. Measure engagement intensity. Track daily active users / monthly active users (DAU/MAU ratio). A ratio above 0.3 in B2B or above 0.5 in B2C indicates strong engagement. Low engagement means users find your product useful but not essential.
4. Iterate on the value proposition. If users sign up but do not retain, your onboarding or core loop is broken. If users do not sign up at all, your positioning or targeting is off. These require different fixes.
5. Expand only after retention is stable. Once your core segment retains well, start testing adjacent segments. Each new segment may require positioning changes but ideally not product changes.
Common Mistakes
Premature scaling. Spending on growth before PMF means you are filling a leaky bucket faster. Every dollar spent on ads before retention is stable is largely wasted. Check your runway and allocate spend accordingly.
Confusing interest with PMF. A viral launch with 10,000 signups is not PMF if Day 30 retention is 3%. Interest validates the problem exists. Retention validates your solution works.
Listening to the wrong users. Free users and power users give different feedback. Focus on the segment you want to build a business around. If your pricing model targets mid-market, weight their feedback heavily and discount feedback from individual hobbyists.
For a deeper treatment of product strategy during the PMF search, read the product strategy guide.