Product–Market Fit Signals
Know when to pour fuel on the fire — and when the engine is not ready.
Metrics in this guide
Each card defines one metric — what it measures, how to calculate it, and a typical benchmark.
- Validation
PMF survey
Sean Ellis PMF score
Share of active users who would be “very disappointed” without the product.
- Formula
- Very disappointed responses ÷ total survey responses
- Typical benchmark
- ≥40% in target segment suggests PMF (Ellis heuristic).
- Validation
Curve
Retention curve shape
Whether cohort retention flattens above zero over time.
- Formula
- Visual: cohort % active over time
- Typical benchmark
- Flat tail >20–30% (varies) beats continuous decay to zero.
- Validation
Organic
Organic / referral growth
Inbound, word-of-mouth, or referral share of new users or pipeline.
- Formula
- Organic new customers ÷ total new customers
- Typical benchmark
- Rising organic share often accompanies PMF in early SaaS.
- Validation
Depth
Depth of use
How intensely loyal users engage vs casual signups.
- Formula
- Power-user actions/week vs median user
- Typical benchmark
- Clear power-user cluster with 5–10× engagement vs median.
PMF signals combine qualitative and quantitative evidence that a segment would be “very disappointed” without your product — notably the Sean Ellis survey (≥40%), retention curve shape, organic growth, and depth of use.
Scaling before fit burns cash and reputation. These signals gate GTM investment and fundraising narrative.
Pre-seed to Series A checkpoints, after major pivots, or when /abtest wins do not move retention.
- Run Sean Ellis survey on active users (last 2 weeks).
- Plot cohort retention — look for flattening.
- Segment PMF score by ICP.
- Check referral and unprompted inbound.
- Document “very disappointed” user profile.
- Decide: iterate, niche, or scale.
- ≥40% “very disappointed” in target segment.
- Retention plateau + clear who loves it.
- Surveying churned users only.
- Declaring PMF from revenue alone.
- One global score hiding weak segments.
Northvale compliance module. Sean Ellis 52% "very disappointed"; retention curve flattening at week 8; depth: 3+ workflows/user. Read: strong fit in pilot segment — not yet across all plant sizes. Run /pmf before national rollout.
PulseWell. Sean Ellis 38% (below 40% threshold); cohort retention improving but W8 still 48%; power users 18% act weekly. Read: not PMF yet — iterate nudge relevance before paid scale.
Harbor reshoring offer. Would buy again 74% in post-workshop survey; referral rate 31%; repeat within 12mo 44%. Services PMF = repeat + referral, not DAU.
Clearwater pilot. Community would miss program 81%; volunteer retention 68% at 90 days; donor would renew proxy 72% from ED interviews. Qualitative PMF strong; instrument /pmf for structured score.
Run /pmf for structured PMF-* artefacts; complement with /feedback and product-health-metrics guide. Lock NSM with /northstar when scaling.
Related techniques
Sources & further reading
- Ellis, S. (2010). Startup Marketing. PMF survey methodology.