What it means
PMF is the inflection most founders chase and most don't reach. The honest test isn't a metric — it's a feeling. Sean Ellis's working proxy: at least 40% of users say they'd be "very disappointed" if they could no longer use the product. Backed up by qualitative signals: organic word of mouth, falling CAC, rising retention, and a sales motion that stops feeling like a fight.
Worked example
Before PMF: the team is convincing every customer. Churn is high. Pricing conversations are painful. After PMF: customers are recommending the product unprompted, the same sales script that used to fail is now closing, and retention curves flatten instead of decaying.
Why it matters
Spending on growth before PMF is the most expensive mistake in early-stage company building. Marketing can amplify pull — it can't manufacture it. Find PMF first; pour fuel on it second.
Common mistakes
- Declaring PMF based on revenue alone, when the revenue is a handful of heroic deals.
- Hiring a growth team to "create" PMF.
- Confusing initial enthusiasm with durable retention.