Oxford Computer Science interview

The Oxford Computer Science interview is academic and run like a short tutorial. You talk through mathematical problems and logic or algorithm puzzles, often with no computing in them at all, while tutors watch how you break a problem into small cases, take hints and justify a general answer. Shortlisted candidates generally have two interviews of about 30 minutes at their first college and at least one at a second, randomly assigned college, online on Microsoft Teams. For 2027 entry most run from 14 to 17 December 2026.

Key facts

What happens in the interview

Oxford Computer Science interviews are academic. An interview may open briefly with what motivates you or something in your personal statement, but most of it is mathematical problems and logic or algorithm puzzles, often with, in the department's words, "apparently no computing content at all". No programming knowledge is assumed, only school maths at about TMUA level.

Tutors run it like a short tutorial:

• They shrink the problem to "an easier problem to start with" and try small numbers.
• They suggest a first step when you're stuck, and ask "what should our next step be?"
• They push you to generalise, from 10 to 11 to n, and ask for a justification or proof.
• They switch questions if one is going in circles, or once it's cracked.

Tutors aren't mind readers, so think aloud, and if you're stuck or unsure what's being asked, ask rather than sit in silence. Slips don't worry them. It's very common not to finish: getting through a significant part of a problem is a strong performance.

You'll work on a shared Miro whiteboard with a stylus, so have a touchscreen of at least 8 inches, a basic stylus, and paper and pens. Leave earlier working visible rather than rubbing it out.

What tutors look for

Oxford's Computer Science tutors look for "ability, potential and commitment". The selection criteria, drawn from the department's published guidance:

• Mathematical ability: accurate, fluent school maths (algebra, counting, inequalities, logs) applied to puzzles and algorithms.
• Absorbing and using new ideas: taking the rules of an unfamiliar game, a definition or a hint, and applying it correctly and systematically.
• Thinking independently: breaking a problem into smaller cases, finding structure (invariants, recursion, a strategy), conjecturing and proving it.
• Perseverance, enthusiasm and interest in computing: staying with a hard puzzle, with a curiosity about the way computers and programs work.
• Explaining your thinking: thinking aloud and justifying answers. A perfect explanation in real time isn't expected.

How the interview is marked

Oxford doesn't publish a marking scale for Computer Science interviews. Tutors score each interview on a numeric scale against agreed descriptors and share it with tutors across colleges, together with your test score and UCAS form. The range, the descriptors and any offer threshold aren't public.

No single interview decides things. It's very common not to reach a complete solution, and getting through a significant part of a problem is a strong performance.

Example questions

These are questions Oxford has published, in the form Toby asks them. Tutors set their own questions, so yours will differ.

Monkey beans

Published by Oxford Computer Science: sample interview problems

An urn contains 23 white beans and 34 black beans. A monkey takes out two beans; if they are the same, he puts a black bean into the urn, and if they are different, he puts in a white bean from a large heap he has next to him. The monkey repeats this procedure until there is only one bean left. What colour is it?

• Why tutors ask it: it shows whether you look for a quantity that never changes instead of simulating every draw, the kind of reasoning used to prove things about programs.
• A hint a tutor might give: "Try tiny urns: one white and one black, then two whites and one black. What is left each time?"
• A strong answer looks for something that stays the same from draw to draw rather than trying to follow all 56 draws, checks each kind of draw in turn, and explains why the order of the draws doesn't matter.
• A common slip is arguing from probability, or from there being more black beans.

Lily-pad lunacy

Published by Oxford Computer Science: sample interview problems

Eleven lily pads are numbered from 0 to 10. A frog starts on pad 0 and wants to get to pad 10. At each jump, the frog can move forward by one or two pads, so there are many ways it can get to pad 10. For example, it can make 10 jumps of one pad, 1111111111, or five jumps of two pads, 22222, or go 221212 or 221122, and so on. We'll call each of these ways different, even if the frog takes the same jumps in a different order. How many different ways are there of getting from 0 to 10?

• Why tutors ask it: it shows whether you can break a counting problem into smaller cases, justify a rule rather than trust a pattern, and adapt your reasoning when the rules change.
• A hint a tutor might give: "How many ways are there to reach pad 1, pad 2 and pad 3?"
• A strong answer starts with the nearest pads rather than trying to list every route to pad 10, explains why each new count follows from earlier ones instead of trusting a pattern, and adapts quickly when the tutor changes the rules, for example by allowing jumps of three.
• A common slip is ignoring order and counting only how many jumps of two the frog makes.

Missing numbers

Published by Oxford Computer Science: sample interview problems

Imagine you are given a list of slightly less than 1,000,000 numbers, all different, and each between 0 and 999,999 inclusive. How could you find (in a reasonable time) a number between 0 and 999,999 that is not on the list?

• Why tutors ask it: it shows whether you can design and compare methods for a large search, describe them precisely enough to carry out, and trade memory against time.
• A hint a tutor might give: "How do you know there is a missing number at all?"
• A strong answer first explains why a missing number must exist, then compares methods by roughly counting their steps. It describes each method precisely enough to carry out, says how much memory it needs, and looks for a way to manage with much less.
• A common slip is answering "the largest number plus one", which fails if 999,999 is on the list.

Practise with Toby

Toby is an AI interviewer that runs practice interviews by voice. The Oxford Computer Science interview is built from Oxford's own guidance and follows the real format:

• First college: first interview. Perhaps a quick word on motivation, then a logic puzzle or strategy problem, solved by trying small cases and building up.
• First college: second interview. A more mathematical or algorithmic problem (counting paths, searching, invariants, recurrences), pushed to a general rule and a justification.
• Second college. One interview with fresh tutors and a fresh problem of either kind.

It draws on 27 problems, each with hints and follow-ups. Eight are questions Oxford has published, and the rest were written to the same style and level, with every result independently re-derived.

Toby puts the problem on screen, gives you time to think and asks you to talk it through. He gives a hint only when you're stuck, asks you to try small cases, and pushes you towards a general rule and a reason why it works. Like a real tutor, he doesn't praise every answer. No programming is needed.

You can add your personal statement so Toby can ask about it, and choose a 10, 20 or 30-minute interview. Your prep page has the format, the department's criteria and practice problems with hints and worked solutions. Afterwards, your debrief gives you a practice mark out of 10 (6 is acceptable, 7 good, 8 strong), a score against each criterion, notes on every question and the full transcript. A practice mark is a guide, not a prediction.

Frequently asked questions

Sources

Last checked October 2026.

• University of Oxford: Interviews
• University of Oxford: Sample interview questions
• Oxford Computer Science: How to apply
• Oxford Computer Science: What tutors look for
• Oxford Computer Science: Formal admissions criteria
• Oxford Computer Science: Sample interview problems
• Oxford Computer Science: Sample interview
• Oxford Computer Science: Admissions feedback 2025-26

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• Cambridge Computer Science interview
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