measuring-product-market-fit

Measuring Product-Market Fit

Scope

Covers

• Measuring PMF using a triangulated signal set (survey + behavior + customer evidence)
• Running and interpreting the Sean Ellis "Very Disappointed" survey (overall + by segment)
• Reading retention curves / cohort retention as PMF evidence (and knowing when they mislead)
• Using reference-customer / advocacy signals as an additional PMF proxy
• Detecting PMF drift (market shifts, rising expectations, competitive resets) and setting a re-measurement cadence
• Special handling for marketplaces (measure PMF per side; focus on the "hard side" first)

When to use

• "Do we have PMF? For which segment?"
• "Run a Sean Ellis PMF survey and tell me what it means."
• "Build a PMF scorecard with retention + survey + references."
• "Our market shifted—did we lose PMF?"
• "We want a go/no-go signal for scaling growth spend or launching publicly."

When NOT to use

• You haven’t defined the problem/ICP yet (use problem-definition).
• You only need a survey instrument, not a full PMF measurement system (use designing-surveys).
• You’re deciding whether/how to pivot (use startup-pivoting) rather than measuring PMF signals.
• You need a product vision/strategy doc as the primary output (use defining-product-vision / ai-product-strategy).
• You already have PMF and need to optimize retention or engagement (use retention-engagement); this skill measures PMF, not post-PMF growth levers.
• You need to brainstorm or validate new startup ideas (use startup-ideation); this skill assumes a product already exists with real users.
• You want to define or refine a north-star metric for an established product (use writing-north-star-metrics); this skill uses metrics as PMF evidence, not as a metric-design exercise.

Inputs

Minimum required

• Product + category + current stage (pre-PMF / early PMF / growth / mature)
• Business model: B2B / B2C / marketplace (and, for marketplaces, which side you’re focusing on)
• Your current best guess at the target segment/ICP (and any meaningful segments)
• Definition of active user and the core value moment (the action that indicates value received)
• What data you can access: survey channels, product analytics, retention cohorts, revenue, qualitative feedback, reference customers/testimonials
• Time horizon and constraints (deadline, privacy/PII constraints, internal-only vs shareable)