Oxford and Cambridge computer science interviews

What is the interview like?

Oxford’s computer science department says interviews happen in December by video call, that candidates generally have two interviews at their first-choice college and at least one at another, and that each lasts around 30 minutes, usually with two interviewers. Some tutors hand out a sheet of problems in advance and others introduce a problem at the start. Most interviews are on 14 to 17 December 2026, with some colleges starting in the week of 7 December, and you will need a touchscreen and a stylus to write on a shared whiteboard.

At Cambridge the department describes how lengths vary by college: Gonville and Caius hold two 25-minute computer science interviews, Peterhouse one in computer science and one in maths, and Churchill one of 30 to 40 minutes. It says your interviewers will give you hints if you get stuck, and that they do not expect you to finish every problem.

What are the tutors looking for?

Oxford’s course page says it looks for proven mathematical talent, the ability to think and work independently, the capacity to absorb and use new ideas, and enthusiasm, and uses these alongside the TMUA to decide whom to interview. At interview, it says, it explores how you tackle unfamiliar problems and respond to new ideas, and it is more interested in how you approach a problem than in the solution. It does not require any formal qualification in computer science.

Cambridge puts the goal of the interview as assessing your academic potential. In practice that means showing your reasoning as you go: try a small example, look for something that does not change, describe the method in words before you commit to it, and say when you think it will not work.

Problems the universities have published

Oxford’s department publishes a set of sample interview problems with short names. In “Monkey beans”, an urn holds 23 white beans and 34 black ones; a monkey takes out two, puts a black bean back if they are the same colour and a white one if they differ, and repeats until one bean is left, and you are asked what colour it is. The trick is to find something that never changes, here whether the number of white beans is odd. In “Missing numbers”, you have a list of slightly fewer than a million different numbers, each from 0 to 999,999, and must find, in a reasonable time, a number that is not on it.

Oxford’s central sample questions add one from a Keble College tutor, a classic logic problem: seven perfectly logical and ruthless pirates must divide 100 gold coins, the most senior proposes a split, and if fewer than half vote for it he is thrown overboard. The tutor says the way in is to solve the case with two pirates and work upwards, and that it shows whether you can break a problem into smaller ones and apply a solution step by step; it also says that if you have questions, you should ask them rather than sit in silence feeling stuck.

The TMUA, the CSAT and written work for 2027 entry

Both universities use the TMUA, sat between 12 and 16 October 2026. At Cambridge, the course page says applicants to Peterhouse or Trinity also take the Computer Science Aptitude Test (CSAT), and Trinity says its candidates sit it immediately before an interview that then discusses how they got on with it. Oxford asks for no written work, and Cambridge does not usually ask for any.

How to prepare

Practise mathematical puzzles out loud rather than programming exercises: counting problems, games where you must find a winning strategy, invariants, recursion and induction, and simple questions about how long an algorithm takes. Oxford’s and Cambridge’s published problems are the right standard, and the TMUA past papers help with the fluency the interview assumes.

Explain each idea before you calculate, try the smallest cases first and say what pattern you see. When you are given a hint, say how it changes your plan. It is fine to take time to think, as long as you tell the interviewer what you are thinking about.

With an account, cookie’s Interview prep runs a mock Oxford or Cambridge interview in this subject with an AI interviewer. It writes problems in the style of the universities’ published examples, not real interview questions, gives a hint when you go quiet and writes a report at the end. It uses credits, and it is for practising beforehand: Cambridge says using AI during an interview is prohibited.