The PhD thesis is the most important part of a doctoral research degree: the culmination of three or four years of full-time work towards producing an original contribution to your academic field.
Your PhD dissertation can therefore seem like quite a daunting possibility, with a hefty word count, the pressure of writing something new and, of course, the prospect of defending it at a viva once you’ve finished.
This page will give you an introduction to what you need to know about the doctoral thesis, with advice on structure, feedback, submission and more.
The first stage of your PhD thesis will usually be the literature review. We’ve already written a detailed guide to what the PhD literature review involves, but here’s what you need to know about this stage of your PhD:
After finishing your literature review, you’ll move onto the bulk of your PhD dissertation. Of course, you’ll eventually return to the lit review to make sure it’s up-to-date and contains any additional material you may have come across during the course of your research.
What sets your PhD thesis apart from previous university work you’ve done is the fact that it should represent an original contribution to academic knowledge. The form that this original contribution takes will largely depend on your discipline.
Depending on the nature of your research, you may ‘write up’ your findings as you go, or leave it until the dedicated ‘writing-up’ period, usually in the third year of your PhD. Whatever your approach, it’s vital to keep detailed notes of your sources and methods – it’ll make your life a lot easier when it comes to using references in your dissertation further down the line.
It’s common to use the terms ‘thesis’ and ‘dissertation’ interchangeably, but strictly speaking there is a difference in meaning between them:
Put simply, you submit a dissertation, but it’s the thesis it attempts to prove that will form the basis of your PhD.
What this also means is that the writing up of your dissertation generally follows the formulation of your thesis (it’s fairly difficult to write up a PhD before you know what you want to say!).
However, it’s normal for universities and academics to use either (or both) terms when describing PhD research – indeed, we use both ‘thesis’ and ‘dissertation’ across our website.
If you’re studying an MPhil, it’s normal to ‘upgrade’ it into a PhD. You may be able to expand on a previous MA or MSc dissertation – or use part of it in one of your PhD thesis chapters. However, you should discuss this with your supervisor and be careful to avoid self-plagiarisation. Similarly, be aware that a PhD is supposed to be a completely original contribution to your field and shouldn’t draw too heavily on work that you’ve already done.
Having completed your initial literature review and conducted your original research, you’ll move onto the next phase of your doctoral dissertation, beginning to sketch out a plan that your thesis will follow.
The exact structure and make-up of your thesis will vary between fields, but this is the general template that many dissertations follow:
PhD thesis lengths vary from subject to subject, but all are far longer than those for undergraduate or Masters degrees. Your university will usually set an upper limit – typically between 70,000 and 100,000 words, with most dissertations coming in at around 80,000 words.
Generally speaking, STEM-based theses will be a little shorter than those in the Arts, Humanities and Social Sciences.
Different universities (and departments) will have different policies regarding what counts towards this word count, so make sure you’re aware what is expected of you. Check with your supervisor whether references, the bibliography or appendices are included in the word count for your dissertation.
There’s no hard and fast rule for the numbers of chapters in a PhD thesis, but most will have four or five chapters (in addition to the introduction and conclusion). This is the sort of thing you’ll discuss with your supervisor when planning out your research – you should agree on a suitable number of topics to tackle in your dissertation during your supervisory meetings.
Once you’ve conducted your research and settled upon your thesis, there’s only one thing left to do: get it down on paper. Appropriately enough, this final part of a PhD is often referred to as the ‘writing up period’.
This is when you produce the final dissertation, which will be submitted as the basis for your viva voce exam. The nature of this task can vary from PhD to PhD.
In some cases you may already have a large amount of chapter drafts and other material. ‘Writing up’ therefore becomes a process of re-drafting and assembling this work into a final dissertation. This approach is common in Arts and Humanities subjects where PhD students tend to work through stages of a project, writing as they go.
Alternatively, you may have spent most of your PhD collecting and analysing data. If so, you’ll now ‘write up’ your findings and conclusions in order to produce your final dissertation. This approach is more common in STEM subjects, where experiment design and data collection are much more resource intensive.
Whatever process you adopt, you’ll now produce a persuasive and coherent statement of your argument, ready to submit for examination.
Your supervisor will usually give you feedback on each chapter draft, and then feedback on the overall completed dissertation draft before you submit it for examination. When the thesis is a work-in-progress, their comments will be a chance for them to make sure your research is going in the right direction and for you to ask their advice on anything you’re concerned about. This feedback will normally be given in the form of a supervisory meeting.
Although your PhD supervisor will be happy to give you advice on your work, you shouldn’t expect them to be an editor – it’s not their responsibility to correct grammatical or spelling mistakes, and you should make sure any drafts you submit to them are as error-free as possible. Similarly, they won’t be willing to edit your work down to fit a particular word count.
When you’ve finished the final draft of your doctoral thesis and it’s been approved by your supervisor, you’ll submit it for examination. This is when it’s sent to the examiners who will conduct your viva.
Submitting your thesis involves printing enough copies for your examiners and the university’s repository. Don’t leave this until the last minute – printing multiple copies of a 300-page document is a substantial undertaking and you should always allow enough time to account for any possible glitches or issues with the printing process.
Your viva will usually take place within three months of submitting your thesis. You can find out more in our dedicated guide to the PhD viva. After your viva, your examiners will give you a report that confirms whether or not you need to make any changes to your thesis, with several different potential outcomes:
Most PhD students will need to fix some corrections with their thesis (hopefully not major ones). It’s very rare for a dissertation to be failed.
Once you’ve made any necessary changes to your thesis, you’ll submit it one last time (usually electronically).
If you have plans to publish all or part of your work, you may want to request an embargo so that it won’t be visible to the public for a certain time. 12 months is a fairly standard time period for this, although you may want to ask for a longer embargo if you know that you want to turn your thesis into a book or monograph.
For more information on what it’s like to do a PhD, read our guides to research proposals, academic conferences and the viva.
Last updated - 16/12/2020
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