How do I know if my D2C brand has actually reached product-market fit, or if I'm just imagining it from a few good sales days?
Run the Sean Ellis 40% test on real repeat buyers, not first-time purchasers: ask "how would you feel if you could no longer buy [product]?" and see what percentage say "very disappointed." Above 40% is a strong signal you have something people genuinely need, not just tried once; below 25% means you're still iterating on the product or the audience, not scaling spend into it. Run this quarterly on a fresh cohort each time (never resurvey the same people) so you can see if the score is trending up as you fix things or quietly slipping as competitors catch up.
Go deeper
3 resources, 3 link-checked.
🛠️ Tool
✓ Link checkedFreeIntermediate
The original Sean Ellis PMF survey, made freely usable - the fastest way to actually run the 40% test on your own repeat buyers instead of reading about it.
A clear step-by-step on running the 40% test correctly - who to survey, when, and how to avoid the sampling mistakes (resurveying the same users, surveying first-timers) that make the score meaningless.
The definitive short book on why customer conversations mislead founders and how to fix the questions you ask - used in accelerator curricula worldwide and directly applicable to a founder doing pre-launch interviews.
