How to know if you have product-market fit
Based on advice from Marc Andreessen, Rahul Vohra (Superhuman) · Updated 2 October 2026
Short answer
Marc Andreessen defined product-market fit as being in a good market with a product that can satisfy that market. The most practical way to measure it is the survey Superhuman used: ask users how they'd feel if they could no longer use the product. If 40% or more say "very disappointed", you likely have it.
Why it matters most
In "The only thing that matters" (2007), Andreessen argues that the market is the most important factor in a startup's success, ahead of the team and the product. Before product-market fit, he says, getting there is the only thing that matters.
He also says you can always feel when product-market fit isn't happening: customers aren't quite getting value, word of mouth isn't spreading and sales cycles take too long.
The 40% survey
Superhuman's founder Rahul Vohra built a product-market fit engine on a test created by Sean Ellis. The survey has four questions:
- How would you feel if you could no longer use the product? (Very disappointed, somewhat disappointed, not disappointed)
- What type of people do you think would most benefit from the product?
- What is the main benefit you receive from the product?
- How can we improve the product for you?
How Superhuman raised its score
- It started at 22% "very disappointed" in summer 2017.
- Segmenting to the users who loved it most raised the score to 33%.
- It then split the roadmap: half on doubling down on what users loved, half on fixing what held others back.
- Within three quarters the score reached 58%.
In your deck
If you run the survey and score 40% or more, that's a strong line for your traction slide, next to your retention.
Read the originals
- The only thing that matters · Marc Andreessen
The 2007 post that defined product-market fit.
- How Superhuman built an engine to find product-market fit · Rahul Vohra (First Round Review)
The full method, from the survey to the roadmap split.
- What is good retention · Lenny Rachitsky
The other half of the evidence: whether users stick around.
Questions founders ask
- What is product-market fit?
- Marc Andreessen's definition: being in a good market with a product that can satisfy that market.
- What is the 40% rule for product-market fit?
- From Sean Ellis's survey: if 40% or more of users say they'd be "very disappointed" without your product, you likely have product-market fit. Superhuman used it to go from 22% to 58%.
- How do I measure product-market fit before revenue?
- Run the Sean Ellis survey with your active users and track the "very disappointed" share over time, as Superhuman did.
Get your deck reviewed the same way.
Comments on every slide, the words to change highlighted, and the 3 fixes that matter.
Keep reading
- What is good retention? Benchmarks by product type
Good and great retention benchmarks from Lenny Rachitsky: 6-month user retention and 12-month net revenue retention for consumer, SMB and enterprise products.
- How to make the traction slide in your pitch deck
What YC says goes on a pitch deck traction slide, with real examples from YouTube, Coinbase, LinkedIn and Uber, and benchmarks for good retention.