How do I prepare for a PhD viva?

The single most useful preparation is rereading the thesis as a critic rather than as its author. Print it, read it over two or three days, and mark every place where you thought "an examiner will ask about this". Those marks are your preparation list, and it is almost always shorter than the anxiety suggests.

Then look up your examiners. Read their recent work in your area, and particularly anything your thesis cites, disagrees with, or should have cited. This is not about flattery. Examiners ask questions from where they stand, and knowing where that is turns unpredictable questions into expected ones.

Do a mock viva, ideally with someone who is not your supervisor, since supervisors know the work too well to ask the naive question that is hardest to answer. The value is not in the specific questions but in practising the experience of speaking about your work under pressure, which is a skill separate from having done the work.

Widen the rehearsal beyond one session. Marino and colleagues recommend practising the defence presentation in front of peers, asking them for feedback and for the questions they would ask, and treating talks at conferences or other research institutes as further practice, especially in front of audiences unfamiliar with your work (Marino et al., 2014, pp. 1-3). They also suggest asking postdocs, collaborators, or peers to read individual chapters for content and logical flow, which surfaces the structural questions an examiner will reach for.

Marino and colleagues also recommend a separate administrative pass, well before the examination. List what your institution requires, including certificates, credit points, seminar attendance, publications, deadlines, the number of thesis copies, formatting, binding, and supporting documents, then keep them in one folder and fix the thesis format early with a template (Marino et al., 2014, pp. 2-3). Check the current rules rather than reusing a file from someone who graduated two years ago.

Prepare a short opening summary and rehearse it aloud until it is comfortable. Many vivas begin with a version of "tell us about your thesis", and starting fluently changes the tone of the whole session.

Then stop. Preparation past a certain point becomes rumination, and arriving rested matters more than one more day of rereading. Take the day before off.

What are the most common viva questions?

Summarize your thesis in a few minutes. Why this question. Why this method rather than the obvious alternative. What is your original contribution. What would you do differently. What are the weaknesses. How does this relate to the wider literature. What next. Prepare all eight.

Write an answer to each, then reduce it to three bullet points. Full scripts are hard to deliver and easy to lose your place in. Bullets keep the structure and let you speak naturally.

The contribution question is the one that decides the outcome, and it is the one most candidates answer vaguely. Have a single sentence ready, then a longer version with the evidence.

Expect scepticism and prepare for it as a normal part of the work. Gu and Bourne describe criticism as the standard response to a new idea, and their advice is to build confidence through clear presentation and a broad knowledge of the related research rather than through defensiveness (Gu and Bourne, 2007, p. 2046). That maps directly onto the eight questions above. For each one, know the alternative the examiner is likely to name, and be able to say what the evidence shows, what remains interpretation, and what you would change.

How long does a viva last?

Usually two to three hours, with wide variation by country and institution. Some run to four hours and a few finish inside ninety minutes. Length is a poor signal of how it is going, since a long viva often means the examiners are interested rather than dissatisfied.

The format varies too. In the UK it is a closed conversation with two examiners. In much of Europe and North America it is a public defence with a presentation and a larger committee. Find out which you are having and what the expectations are, because preparing for the wrong one is a real risk.

Treat published advice on graduate examinations as transferable rather than binding. Gu and Bourne write from more than 25 years of experience as students and mentors, and they state plainly that programme length, evaluation methods, and institutional structures differ across countries (Gu and Bourne, 2007, p. 2045). So confirm your own format, presentation requirements, permitted materials, and likely order of questioning with your supervisor or a recent graduate from your department, not with a guide written for a different system.

Take your annotated thesis, a notepad, water, and a list of your own corrections. Being able to say that you have already noticed an error, and where, is a good position to be in when an examiner raises it.