JANE STREET TRADING INTERVIEW GUIDE

It is rare for a firm to warn you off its own internet folklore. Take the hint, and spend the time you would have spent on forum threads on probability instead.

Checked against Jane Street's interviewing pages in September 2026. The firm publishes its own interview guidance and mock interview videos, and says the structure varies by discipline. It also tells candidates plainly: "Don't believe everything you read" about its process. Old forum threads describing an exact sequence of rounds should be treated accordingly.

You are not being tested on finance

This is the single most useful thing the firm states, and the thing candidates most often get wrong. For quantitative trading they say a problem-solving mindset is required and a finance background is optional, and that they will not test knowledge of finance or economics.

So reading about option greeks the week before will not move your outcome. Getting faster and calmer at probability under time pressure will.

Collaborative problem solving is the format

The firm describes its interviews as collaborative problem solving, and says asking good questions matters more than arriving with every answer. That has a practical consequence: silence is expensive. An interviewer cannot evaluate reasoning they cannot hear.

A workable habit is to narrate in three beats. State your read of the problem, state the approach you are choosing and why, then compute. If you get stuck, say what you are stuck on. That is a question, and questions are explicitly welcome here.

What to train

• Probability and expected value. The load-bearing skill. Conditional probability and EV comparisons come up constantly in trading conversations.
• Estimation. Being willing to produce a defensible approximate number, and to say what would sharpen it.
• Games and betting logic. Pricing a payoff, deciding whether to take a bet, and noticing when the other side knows more than you.
• Mental arithmetic. Not as a party trick. As the thing that frees your attention for the actual reasoning.
• Thinking out loud. Practise this deliberately; it is the format, not a bonus.

Representative practice questions

These are original representative questions, not Jane Street questions.

1. I roll a fair die. You may take the value, or pay $1 to reroll once. What is the reroll worth?

   Rerolling is worth it when the first roll is below the expected value of a fresh roll, 3.5. Rerolling on 1, 2, or 3 gives an expected gain worth roughly (1/2) × 1.5 = 0.75 before the fee, so at $1 it is close to a decline. Show the comparison, not just a verdict.

2. Two players alternate flipping a fair coin; first head wins. What is the chance the first player wins?

   1/2 + 1/8 + 1/32 + … = 2/3. Recognising the geometric series quickly is the point.

3. You are offered a bet at even money that a random person in the room shares your birthday month. Take it?

   Roughly 1/12 per person, so no, unless the room is large. Ask how many people are in the room before answering. That question is part of the answer.

4. Estimate how many bicycles are in a city of two million people.

   Build a small model out loud: households, bikes per household, adjustment for climate and density. Then say which assumption your answer is most sensitive to.

How to prepare

Use the firm's own published materials first; they are the only primary source. Then train the skills with the probability question bank, expected value questions, and the estimation guide.

Source: Jane Street, Interviewing, checked September 2026.