Sample Questions for the Y Combinator Interview

What are you making?

Some variant of “what are you making”, “what are you working on”, or “what are you going to build” is a common first interview question.

Your Numbers

Know your numbers cold.

  • How many users have ever engaged
  • How many currently active users
  • Total revenue
  • Total costs, fixed and marginal
  • Acquisition funnel conversion rate
  • Customer acquisition cost
  • Growth rates of all of the above

Value Prop

  • Who needs what you’re making?
  • What’s new about what you make?
  • What are the top things users want?
  • What are your users doing now?
  • How does your product work in more detail?

Market Size

  • How many people are in your target market?
  • How many $B is the market?
  • How fast is the market growing?
  • Who are your competitors? Who might become competitors?
  • Which competition do you fear most?
  • How many users do your competitors have?
  • How much are your competitors making?
  • How much time and money do users in your target market waste before switching to your product/service?
  • What are some trends in your target market, and related markets?

User Acquisition

  • Who is going to be your first paying customer / who was your first paying customer?
  • How do you get users?
  • How do users know they need this?
  • What exactly makes you different from existing options?
  • How will users find out about you?
  • What makes new users try you?
  • What makes new users reluctant to try you?
  • How will you overcome that resistance?


  • What’s an impressive thing you have done?
  • Tell us something surprising that has happened.
  • What’s the biggest mistake you have made?

Founder-Market Fit

  • Why did you choose this idea?
  • Why are you uniquely qualified to work on this?
  • Why do you want to dedicate your life to working on this?

Growth Potential

  • How will you make money?
  • How much money could you make per year?
  • How does this become a billion-dollar company?
  • If your startup succeeds, what additional areas might you be able to expand into?


  • Why did your team get together?
  • Who is “the boss”?
  • Who will be your next hire?
  • How do we know your team will stick together?


  • What’s the rocket science here?
  • What part of this are you going to build first?
  • What have you learned so far from working on this idea?
  • Why isn’t someone already doing this?
  • What are the key things about your field that outsiders don’t understand?
  • What keeps you up at night?
  • What obstacles will you face and how will you overcome them?
  • Six months from now, what’s going to be your biggest problem?
  • What’s the funniest thing that has happened to you?
  • Are you open to changing your idea?
  • Have you considered [some twist on your idea]?



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Liron Shapira

Liron Shapira

Founder/CEO of Relationship Hero