Product-Market Fit (PMF) is the moment when your product satisfies strong market demand. Marc Andreessen defined it as "being in a good market with a product that can satisfy that market." It's the most important milestone for any startup.
Before PMF, focus on learning. After PMF, focus on growth. Spending on growth before PMF is the #1 cause of startup death.
Sean Ellis proposed a quantitative PMF test: ask users "How would you feel if you could no longer use this product?" If ≥40% say "Very disappointed", you have PMF.
PMF Score (Sean Ellis Test)
PMF = % of users who would be "very disappointed" without the product
≥40% = PMF achieved. 25-40% = getting close. <25% = not yet.
Qualitative signs of PMF:
- Users tell others without being asked (organic word-of-mouth)
- Usage grows without marketing spend
- Users complain when the product is down
- Sales cycles are shortening
- Retention rates are high and stable
Key Takeaways
- PMF = strong market demand for your product.
- Sean Ellis Test: ≥40% "very disappointed" = PMF achieved.
- Don't invest in growth before achieving PMF.
- Both quantitative (survey) and qualitative (behavior) signals matter.