It is the question every student asks their supervisor, and the answer is almost always some version of “as long as it needs to be” — which is true, and completely useless when you are staring at a word count.
So here is a more practical answer to how long should a literature review be, along with the reasoning behind it, so you can work out the right length for your own project rather than borrowing someone else’s number.
The short answer
For most dissertations and theses, the literature review runs to roughly 20–30% of the total word count.
That gives you:
- 8,000-word dissertation — around 1,600 to 2,400 words
- 10,000-word dissertation — around 2,000 to 3,000 words
- 15,000-word masters dissertation — around 3,000 to 4,500 words
- 80,000-word PhD thesis — often a full chapter of 12,000 to 20,000 words, sometimes split across two
A standalone literature review essay, set as its own assignment, is different again. Those are usually 1,500 to 3,000 words and the brief will normally tell you.
Now the important caveat: your handbook overrides all of this. If your department specifies a chapter breakdown, follow it precisely. Some courses want 40%. Some want 15%. Neither is wrong at that institution.
Why the percentage varies so much
The length of your review is really a function of what your project needs, not a fixed proportion.
You will need a longer review if your topic sits across two or more fields, if there is a long history of research you need to trace, if you are arguing that existing work is flawed, or if your study is theoretical rather than empirical. Theory-heavy projects sometimes run to 40% or more, because the review is much of the contribution.
You can get away with a shorter one if your topic is narrow and recent, if your project is mostly practical or design-based, or if the field genuinely is small. Some emerging topics have thirty relevant papers in total, and padding a review to hit a percentage is worse than writing a tight one.
How many sources is enough?
Rough guidance, and it is only rough:
- Undergraduate dissertation — 25 to 40 sources
- Masters dissertation — 40 to 70
- PhD thesis — well over 100, often several hundred
Do not treat these as targets to hit. A review citing thirty papers that genuinely shaped your thinking reads far better than one citing eighty, sixty of which appear once in a list and never again.
Markers can tell the difference immediately. A source you have actually read gets discussed, compared or challenged. A source you have padded with gets a single passing mention.
The real problem is usually structure, not length
When a supervisor says a review is too long, they often mean it is repetitive. When they say it is too short, they usually mean it is shallow. In both cases the word count is a symptom.
The most common structural failure is what markers sometimes call the annotated bibliography problem: paragraph after paragraph that goes “Smith (2019) found X. Jones (2020) found Y. Patel (2021) found Z.” Each one summarised in turn, none of them connected.
That structure eats words at an alarming rate and says almost nothing. It also caps your mark, because summarising is a lower-order skill than synthesising.
The fix is to organise by theme or debate, not by author. Instead of a paragraph per study, write a paragraph per idea, and bring several studies into it:
“Research on this question splits along methodological lines. Studies using self-report measures consistently find a strong association (Smith, 2019; Patel, 2021), while those using observational data report a much weaker effect (Jones, 2020). This divergence suggests the relationship may be partly an artefact of how it is measured.”
Three sources, one paragraph, and an actual argument. The author-by-author version would have taken three paragraphs to say less.
What has to be in there
However long yours ends up, a review is expected to do four things:
- Map the field. What is already known, and who established it.
- Group and compare. Where scholars agree, where they disagree, and why.
- Evaluate. Which studies are convincing, which have methodological problems, and how you know.
- Identify the gap. What has not been settled — and this gap must be the thing your study addresses.
That last point is the one students most often miss. Your review is not a neutral survey. It is the argument for why your research needed doing. If a reader finishes it without understanding why your study exists, it has not done its job, no matter how many sources it cites.
Trimming a review that has run long
If you are over, cut in this order:
Background that belongs in the introduction. General scene-setting about why the topic matters usually is not review material.
Studies that agree with each other. If five papers found the same thing, cite all five in one bracket and discuss one in detail. You have lost nothing.
Method descriptions. You rarely need to explain how a study you are citing was conducted, unless the method is the point you are making about it.
Long quotations. Paraphrase and cite. A quotation should earn its place because the exact wording matters, not because it fills space.
Definitions of common terms. Your marker knows what your field’s basic vocabulary means.
Padding a review that is too short
If you are genuinely under length, resist the urge to add more summaries. Add depth instead.
Go back to the studies you have already cited and evaluate them properly — sample sizes, contexts, limitations, whether the findings transfer to your setting. Look for the counter-argument you have not represented. Widen slightly into an adjacent field and explain the connection. Trace how thinking on your question has changed over time.
All of that adds words while also adding marks. More summaries add words and nothing else.
One last check before you submit
Read your review and ask whether someone unfamiliar with your topic would finish it able to say, in one sentence, what your study is going to do and why nobody has done it yet.
If yes, the length is right, whatever the number says. If no, more words will not fix it.
If you are stuck
Literature reviews are the chapter students most often rewrite two or three times, usually because the structure was wrong rather than the reading. Reorganising round themes rather than authors solves most of it.
If you would rather have help, our dissertation writing help covers literature reviews specifically, and we work on thesis writing at masters and doctoral level too. There is a related guide on structuring your methodology chapter, which is usually the next thing you will be writing.