Citadel Securities Quantitative Trader intern 2028 trader interview guide

For
2028 summer analysts
Sources
10 cited

Passed the Citadel Securities math test? This page covers the trader interviews for the Quantitative Trader internship (US), summer 2028: one or two phone or video calls of about 45 minutes with a trader, on probability, expected value, Fermi markets and your resume.

A student seated at a desk in a small dorm room on an evening phone call, earbuds in, two dice and a sheet of rough tree diagrams on the desk, a warm desk lamp and dark campus trees outside the window.
Citadel Securities trader interviews have run about 45 minutes each, with a trader, by phone or video, after a timed math test.

Key facts

  • How many: Usually two rounds with traders: two before an in-person superday in Oct 2025 (summer 2026), and two in Aug 2026 (summer 2027). The Aug 2022 (summer 2023) and Aug 2024 (summer 2025) New York applicants stopped after one phone interview with a trader.10,7,8,4,5,6
  • Length and format: A phone or video call of about 45 minutes with a trader: 45 minutes of math and logic in Aug 2022 (summer 2023), two 45-minute rounds in Oct 2025 (summer 2026).4,7,10
  • What they ask: Probability, expected value and logic, your resume, and market making from the first rounds: a market on a Fermi estimate, then spread and size (Aug 2026, summer 2027).4,6,8,10
  • Before it: Most applicants take a timed math, probability and statistics test first, about a week after applying. A summer 2027 applicant had a first round in Jul 2026 with no test.4,5,6,10
  • Who interviews: Every trading interview is with a trader. Which trader you get shapes the questions, so prepare across topics rather than for one question.4,5,10
  • When: For summer 2027, first-round interviews ran from mid-July to the end of September 2026, and whole processes took under a month (Oct 2025, summer 2026; Aug 2026, summer 2027).10,7,8

One application covers trading and quantitative research. On the quant research side the first round is a 45 to 60 minute video interview with a CoderPad link; the trading rounds lean on probability and markets instead.1,3,10

What the Citadel Securities interview looks like

  1. Where it sits

    You apply on the shared trading form, then most applicants take a timed math, probability and statistics test about a week later. Pass it and the trader interviews follow: one call in some processes, two in others, then a superday. A summer 2027 applicant went straight to a first round in Jul 2026 without the test.1,4,5,6,7,10

  2. The format

    Expect a phone or video call of about 45 minutes with one trader. The Aug 2022 (summer 2023) phone screen was 45 minutes of math and logic, and the Oct 2025 (summer 2026) process had two 45-minute rounds before an in-person superday. The firm's campus interview guide says it interviews on weekdays, in business hours.4,7,10,3

  3. What they ask

    Probability, expected value and logic, with your resume along the way. Market making starts early: in Aug 2026 (summer 2027) the first round set a market on a Fermi estimate and a probability problem, and the second a game theory question on how to set your spread and size. An Oct 2025 (summer 2026) process asked a Bayes bet on stones drawn from a bag.4,6,8,9,10

  4. How to answer

    Talk through your thinking. The firm's campus interview guide says its technical interviews are practical and problem-solving oriented: take time to assess a problem, ask clarifying questions, discuss trade-offs, say what you do and do not know, and take hints. Its traders value taking in new information and acting quickly, so update your answer out loud when the interviewer adds a twist.3,2

  5. After it

    Next is the superday, in person or as a virtual onsite, with more market making. The Oct 2025 (summer 2026) and Aug 2026 (summer 2027) New York processes each took under a month in all.7,8,10

Before your trader interviews

  • A quiet room, a charged phone and a tested camera; have paper and a pen within reach.
  • Conditional probability and Bayes until the setup takes seconds.
  • Expected value games with dice, coins and cards, including the follow-up twists.
  • Fermi estimates broken into pieces, then turned into a bid, an ask and a size.
  • One line on how you would widen or tighten a quote after a trade.
  • A 60-second walk through your resume, leading with the most quantitative lines.
  • Why Citadel Securities and why trading, tied to a project or competition of your own.
  • Your top two coding languages from the form, ready in case a round turns to code.

The questions

Expect three strands in a 45-minute call: probability and expected value worked out loud, a market on something uncertain, and your resume and motivation. The questions vary with the trader, so cover all three.4,5,6,8,10

  • Probability: Bayes, conditional probability and counting, worked out loud with follow-ups.
  • Expected value: Dice, coin and card games: what is it worth, and would you play.
  • Market making: A bid, an ask and a size on an estimate, then spread and size as the game changes.
  • Fermi estimates: A rough number for something you cannot look up, given as a range.
  • Resume and motivation: Your projects and coursework, why trading and why Citadel Securities.

Which division question you get

Quantitative Trading, New York
Aug 2022 (summer 2023): 45 minutes of math and logic with a trader. Aug 2024 (summer 2025): resume and expected value questions. Oct 2025 (summer 2026): two 45-minute rounds of very hard math. Aug 2026 (summer 2027): a market on a Fermi estimate and a probability problem, then game theory on spread and size.4,6,7,8
Quantitative Research (same application)
A 45 to 60 minute video round with a CoderPad link: programming, research ability, data structures and algorithms, problem solving, plus your internships, projects and reasons for Citadel Securities.3,1
Credit & Rates Rotational TradingBest guess
Expect the same probability and market-making core, plus a question or two on how rates and credit spreads move.

The Credit & Rates line is our best guess from the desk's place on the shared trading form and the other trading rounds.

Example questions and how to answer them

Market making"Make me a market on how many commercial flights take off in the US in a day."8,10
  1. 1Break the number into pieces you can guess: people, trips a year, passengers per flight.
  2. 2Multiply through with round numbers, out loud.
  3. 3Turn your doubt into a width: quote a bid and an ask, and a size.
  4. 4When the trader buys or sells, say what it tells you and move your quote.

Tip: In Aug 2026 (summer 2027) a New York first round built its market-making question on a Fermi estimate. The width of the quote matters as much as the middle.

Example answer, written by Intervyo (not a real candidate)

Written by Intervyo as an example. Say 330 million people take about 2.5 flights a year each, so roughly 800 million passenger trips, or about 2.2 million a day. At around 100 passengers a flight that is about 22,000 flights. My passengers-per-flight guess could be off by a third either way, so I will make it 17,000 at 28,000, for 10 lots. If you buy at 28,000, I will ask myself whether you know regional jets are smaller than I assumed, and move up to 20,000 at 31,000.

Probability"A bag holds four stones, each black or white, with every count of black stones equally likely. You draw two and both are black. What is the chance the next one is black, and would you bet on it at even odds?"9,7
  1. 1Set the prior: 0 to 4 black stones, each one in five.
  2. 2Weight each count by the chance of two blacks first; 0 and 1 drop out.
  3. 3For each count left, find the chance the third stone is black.
  4. 4Combine, then turn the probability into a bet: price, edge and size.

Tip: An Oct 2025 (summer 2026) New York process asked an extended Bayes question on black and white stones in a bag, then asked for a bet. The equal-chance prior is our assumption; ask the interviewer what to assume, and finish with the bet, not just the number.

Example answer, written by Intervyo (not a real candidate)

Written by Intervyo as an example. Two blacks first has chance 2 in 12 with two black stones, 6 in 12 with three and 12 in 12 with four, so the weights are 2, 6 and 12 out of 20. With two black, the next stone cannot be black; with three it is black half the time; with four always. So the chance is (2 x 0 + 6 x 0.5 + 12 x 1) / 20 = 3/4. At even odds I win $1 three times in four and lose $1 once, an edge of 50 cents a dollar, so I bet, and I would size it so a loss does not hurt.

Expected value"You turn over cards from a shuffled deck one at a time. How many cards do you expect to turn before the first ace? What about the first heart?"10
  1. 1Picture the 4 aces splitting the other 48 cards into 5 gaps.
  2. 2Each gap holds 48 / 5 cards on average, so the first ace comes after about 9.6 cards.
  3. 3Add one for the ace itself if they ask where it lands.
  4. 4Reuse the rule for the twist: 13 hearts split 39 cards into 14 gaps.

Tip: The trader rounds and the superday keep coming back to probability, expected value and brainteasers, up to hard probability in later rounds. Name the general rule so each twist is quick.

Example answer, written by Intervyo (not a real candidate)

Written by Intervyo as an example. The four aces cut the 48 other cards into five gaps of 9.6 cards on average, so I expect 9.6 non-aces before the first ace, and the ace lands at card 10.6. For hearts, 13 hearts cut the 39 others into 14 gaps of about 2.8, so the first heart lands at about card 3.8. The rule is (N + 1) / (k + 1) for the position of the first of k marked cards in N.

Game theory"How would you set your spread and size in this game?"8,2
  1. 1Start from fair value and how sure you are of it.
  2. 2Widen the spread when the other side may know more than you.
  3. 3Size down when one bad trade could hurt; size up when your edge is clear.
  4. 4Say how both change after each trade and each new piece of information.

Tip: This was the second round of a New York trading process in Aug 2026 (summer 2027). The firm's traders talk about taking risk in uncertain conditions, so explain why, not just what.

Resume and motivation"Walk me through your resume, and why Citadel Securities?"6,3,1
  1. 1School, major and year in one line.
  2. 2Two or three entries, the most quantitative first, with one result each.
  3. 3Why trading: a project, competition or game that taught you to decide under uncertainty.
  4. 4Why Citadel Securities: trading across options, ETFs, equities, fixed income, commodities and currencies, two summer rotations, and mock trading and game theory sessions.

Tip: An Aug 2024 (summer 2025) New York phone call with a trader asked about the resume before the expected value questions. The firm asks you to know why you want to work there and to refine your own story.

More Citadel Securities interview questions

Probability and expected value

  • “Counting, probability and logic, worked through with a trader.”4

    New York, Aug 2022 (summer 2023); topics only

  • “Expected value questions after the resume.”6

    New York, Aug 2024 (summer 2025); topic only

  • “An extended Bayes question on stones in a bag, then a bet on the next draw.”9,7

    New York, Oct 2025 (summer 2026); the listing does not say which round

Market making

  • “Make a market on a Fermi estimate.”8

    First round, New York, Aug 2026 (summer 2027); wording ours

  • “How would you set your market's spread and size?”8

    Second round, New York, Aug 2026 (summer 2027)

Resume and motivation

  • “Walk me through your resume.”6

  • “What are your reasons for exploring opportunities at Citadel Securities?”3

    Quant research first round

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How long to hear back after the interview

The test link has come within about a week of applying, and the trader rounds and superday have followed inside a month in recent New York processes. Some took one to two months.4,5,7,8,6

  1. Aug 2022 (summer 2023)

    Quant trader intern, New York

    An online test within a week of applying, then a 45-minute technical phone screen on math and logic with a trader, where the process ended. One to two months.4

  2. Aug 2024 (summer 2025)

    Quant trader intern, New York

    Applied by referral, took the math test a week later, then a phone interview with a trader, where the process ended. Under a month.5

  3. Aug 2024 (summer 2025)

    Quant trading intern, New York

    Heard back within a month with a timed test, then a phone call with a trader on the resume and expected value. One to two months.6

  4. Oct 2025 (summer 2026)

    Quant trader intern, New York

    A test with coding and probability, two 45-minute interviews, then an in-person superday weighted toward market making. Under a month.7

  5. Jul 2026 (summer 2027)

    Summer 2027 internship applicant

    A first-round interview with no online test before it.10

  6. Aug 2026 (summer 2027)

    Student, trading, New York

    Through a recruiter: a market on a Fermi estimate and a probability problem, then a second round on game theory, spread and size. Under a month.8

Tell your recruiter about a competing offer or a later-stage process as soon as you have one; the firm says it does its best to meet your deadline.3,1

Best guessIf a week passes after a trader round with no news, check your email filters, then send your recruiter one short note.

What happens after the interview

  1. Online application

    One shared trading form across Citadel and Citadel Securities, with a resume, education history and short questions.1

  2. Online math test

    Usually a timed math, probability and statistics test, about a week after applying.4,5,6,10

  3. Trader interviews (1 or 2)You are here

    This page. One or two phone or video interviews of about 45 minutes with traders: probability, expected value, market making and your resume.4,6,7,8

  4. Superday

    In person in Oct 2025 (summer 2026) and weighted toward market making; some processes run it as a virtual onsite.7,10

  5. Offer

    A decision has come about a week after a virtual onsite, then two summer rotations ahead of full-time placement.10,1

Trader interviews vs superday

The trader interviews are one or two calls that decide who reaches the superday. The superday is several interviews in a row and leans harder on market making.

Format

Trader interviews

Phone or video, about 45 minutes each.4,7,10

Superday

In person in Oct 2025 (summer 2026); in other processes a virtual onsite of several 30- to 45-minute rounds.7,10

Count

Trader interviews

One or two rounds.5,7,8

Superday

Several interviews on one day.10

Content

Trader interviews

Probability, expected value, Fermi markets and your resume.4,6,8

Superday

More market making, on a solid base of math and statistics.7

Who

Trader interviews

One trader per round.4,5,10

Superday

Traders across the day.10

2028 summer analyst status

For summer 2027 the US posting was online by Jul 6, 2026, and first-round interviews ran from mid-July to the end of September 2026. Expect summer 2028 trader interviews from around mid-July 2027.10

FAQ

How many trader interviews does Citadel Securities have?

One or two before the superday. New York accounts from Aug 2022 (summer 2023) and Aug 2024 (summer 2025) stopped after one phone interview with a trader; the Oct 2025 (summer 2026) and Aug 2026 (summer 2027) processes had two rounds.4,5,6,7,8

Is the first round on the phone or on video?

Either. Trading rounds have been phone calls with a trader and are described as phone or video; the quant research first round on the same application is a video call with a CoderPad link. Test your camera either way.4,5,10,3

What do Citadel Securities traders ask in the first round?

Probability, expected value and logic, your resume, and market making: in Aug 2026 (summer 2027) a market on a Fermi estimate, then spread and size in the second round. An Oct 2025 (summer 2026) process asked a Bayes bet on stones in a bag.4,6,8,9

How long is a Citadel Securities trader interview?

About 45 minutes. The Aug 2022 (summer 2023) phone screen was 45 minutes of math and logic, and the Oct 2025 (summer 2026) process had two 45-minute rounds.4,7

Is there coding in the trader interviews?

Prepare for it lightly. The trading rounds in the New York accounts are probability and markets, but the Oct 2025 (summer 2026) test before them mixed coding and probability, and the form asks for your top two coding languages for interviews.7,1,10

How should I prepare for the Citadel Securities trader interviews?

Drill probability and expected value out loud, practice quoting a market on a Fermi estimate and updating it, and have a short resume walk-through. The firm's guide says to share your thinking, ask clarifying questions and take hints.3,8,10

Interview at other firms

Sources

Firm pages first, then dated candidate reports. Last checked Nov 9, 2026.

  1. 1Citadel Securities: Quantitative Trader - Intern (US) (Trading and Research), posting and application form
  2. 2Citadel Securities: Candidate FAQs: Markets & Trading
  3. 3Citadel Securities: Our Campus Quantitative Research Interview Process (Nov 2024)
  4. 4Candidate report on a public forum: Quant Trader Internship interview, New York (Aug 2022)
  5. 5Candidate report on a public forum: Quant Trader Intern interview, New York (Aug 2024)
  6. 6Candidate report on a public forum: Quant Trading Intern interview, New York (Aug 2024)
  7. 7Candidate report on a public forum: Quant Trader Intern interview, New York (Oct 2025)
  8. 8Candidate report on a public forum: Trading interview, New York (Aug 2026)
  9. 9Candidate reports on a public forum: Citadel Securities interview questions (company database)
  10. 10Trading Interview: Citadel Securities Internship 2027: Pay, Roles And Interview Process · prep site

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