What to prepare for a Y Combinator interview

To prepare for a Y Combinator interview, write down crisp two-sentence answers to the questions partners nearly always ask, rehearse them with someone who interrupts you, and make sure every founder knows the metrics without looking anything up. The interview is a fast conversation, not a pitch, so the aim is to reach the interesting part of your company within the first minute. Separately, get your incorporation, founder stock and IP paperwork straight, since a yes leads quickly to documents.

How does the YC interview actually run?

The format has been stable for years even as the batch calendar has changed. You are invited after the written application and video are reviewed. The interview itself is short and dense.

Partners usually open with “what are you working on?” and then follow whatever is most interesting or most doubtful. You will rarely get through a prepared answer before the next question. That is not a bad sign. It usually means they have understood and want to test something else.

YC publishes the current batch dates and deadlines on its site, and the schedule has shifted more than once, so check the dates there rather than relying on an older blog post.

Which questions should you prepare for?

The questions are predictable in theme, if not in order. The table groups the ones founders report most often, with what the partner is really trying to learn.

Write your answer to each in two sentences. Then cut it down. A good answer starts with the fact and adds the reason, for example: “We have 31 paying dental clinics in Ohio. Twenty came from referrals by the first five.” A weak one starts with background and reaches the number at the end, by which time the partner has interrupted.

What numbers should every founder know cold?

Partners ask for numbers without warning and notice when founders look at each other before answering. Agree the definitions in advance so you never give two different figures on the same call.

The numbers you should have ready about your own company:

• Users or customers today, and what counts as one.
• Revenue, monthly, and whether it is recurring.
• Growth rate, week on week or month on month, over a stated period.
• Retention, even a rough one: of the users who started in a month, how many are still active.
• Cash and burn, and how many months that gives you.
• Money raised so far, from whom and on what instrument.

If a number is small, say it plainly. “Four pilots, none paying yet” is a fine answer. A rounded-up number that falls apart under a follow-up question is not.

How do the deal terms change your cap table?

The standard deal combines a post-money SAFE for 7% and an uncapped SAFE with a most favored nation clause, which converts on the terms of the lowest-cap SAFE issued afterwards until the priced round. On YC’s own example, with a $15 million post-money cap on later SAFEs, the $375,000 converts to 2.5%.

It is worth seeing what that does to founder ownership before you are in the room, because partners sometimes ask what you plan to raise after Demo Day. Put the YC investment and any later raise into the dilution calculator to see the founders’ stake after each step.

The method is explained on the round dilution tool page. For the conversion of each SAFE in more detail, the SAFE conversion calculator handles caps and discounts.

How should cofounders split the interview?

There is no rule about who answers what, but there are clear signs of a weak team on the call: one founder answering everything, founders correcting each other on numbers, or a technical founder who cannot describe the customer.

A simple approach works for most teams:

• The founder closest to customers takes the opening “what do you do” question.
• The technical founder takes product and architecture questions, but can also say who the first users are.
• Either founder can answer any numbers question, which is why the definitions are agreed beforehand.
• Nobody reads from notes. A one-page cheat sheet out of sight is fine for checking a figure.

If you are a solo founder, prepare for the question about cofounders. Partners will ask why you are building alone and how you plan to cover what you cannot do. A straight answer with a plan is better than defensiveness.

What should you have ready if they say yes?

YC moves quickly after acceptance, and the deal documents are standard. What slows founders down is their own paperwork. YC generally invests in companies in a short list of structures, most commonly a Delaware C corporation; if you are an LLC or a foreign company, expect a conversion or a flip, which takes time and tax advice.

Founders who have this in a tidy folder before the interview can sign the week of acceptance. The accelerator applications page lists the same documents and the rooms that suit a short, structured process like this one. The full stage-by-stage list is on the startup data room checklist.

What mistakes cost founders the interview?

Most rejections have nothing to do with preparation, and some good companies are turned down. But some failures are avoidable, and partners and alumni describe the same ones again and again.

1. Too much background. Starting with the history of the industry instead of what you make.
2. Vague users. “Small businesses” instead of “independent bike shops with two to five staff”.
3. Inflated numbers. Any figure that changes when a partner asks a second question.
4. Defensive answers about competition. “Nobody else does this” invites the partner to name three companies.
5. No plan for the batch. Not knowing what you would measure at the end of the three months.
6. Arguing with feedback. Partners sometimes push back to see how you react. Listen, answer once, move on.

How should you practise?

Practice is where most of the gain is. The aim is not a script; it is getting used to speaking about the company in short, factual sentences while being cut off.

After the interview, write down every question you were asked. Whatever the outcome, that list is useful the next time you talk to an investor, and many founders who are turned down reapply with a stronger company.