Every time I ask my students whether they have any questions about their upcoming essay submissions, without a shadow of a doubt I'll be asked (possibly more than once, in various forms) how many references they need to have.
It sounds like a simple question, and it has a simple answer: it depends.
But that's not a particularly helpful answer on its own, so in this article I'm going to set out a few different guidelines on when and why you should reference that should then allow you to know the answer to the question "how many citations is enough?".
If you came here for the number alone, the answer I come to a bit later is about one peer-reviewed reference for every 200 words of essay body, based on the body being 75% of the word count. That's a very rough and ready figure, and more importantly it's answering the wrong question. You'll do a lot better if you read on and find out why. The advice I'm about to give will probably push you up 5-10 marks, if you follow it in your next assignment.
1. Why you need to have references
Fundamentally, references are a way of acknowledging work that has been done before yours, as well as a way of showing where your evidence for a particular claim is coming from. A lot of students worry that citations are mainly a way of catching them out: that their lecturers or tutors or examiners are looking for places in which they've failed to read the things that they should have read, and to dock them marks accordingly.
But that's not what they're for. Yes, there will be instances in which there's some seminal work in a field that you probably ought to read, but it's not always your fault if you don't know that it exists and therefore haven't cited it. It's not plagiarism if you come up with an idea on your own which someone else has come up with before. Instead, the reason that your examiner is going to point out where something has been said before is so that you can benefit from others' work by reading what may well be a more nuanced and fleshed-out version of the argument that you're making (after all, someone probably got paid to write it).
That means you should have references where you've used someone else's work to inform your own ideas.
In addition, you should have references when you're making an empirical claim (one that is based on observations about the world) and you need to back that claim up. For example, you might make the claim that there are a thousand chickens stolen from farms around the world every day. It would have to be common knowledge for you to be able to say that without a citation. Because it's unlikely to be common knowledge, you should have some kind of source that you're drawing upon. That means that someone who came along and read your work and wanted to scrutinise the argument that you were making could then go to that source and find out if it says what you claim it does.
2. "What if I'm building on their ideas?"
Now that I've told you that you need to cite other authors when you've read their work and used it to build up your own argument, you might well ask whether that's still necessary if you used their thoughts but now you're going further and creating your own ideas.
The answer is yes, and indeed the answer is that this is probably the optimal way to use a source in most essays. This is because rather than just saying "Jones (1999) claims that chicken theft is a significant issue in agricultural communities", you can say all that followed by, "I go further than Jones, showing why this is not just an issue in farming communities but in all communities, even in countries that are not reliant on primary sector industry." That shows not only that you've read the literature, but that you're using it to inform your own argument.
So, you should reference an author even if you're going beyond what they've said.
3. Make sure the references are doing work
When people ask how many references they ought to have, what they're really trying to ask is often "how much reading do I need to do?"
If that's not the question you're asking, and you genuinely think that markers just go through your bibliography and count the number of sources as a heuristic for the quality of your grade, then I'm here to tell you that you're mistaken. You shouldn't just be dropping references into your work if they're not doing anything. You don't need to reference the Oxford English Dictionary in order to define every single word (or indeed any word - seeing a dictionary reference actually activates the gag reflex in most lecturers). Likewise, you don't need to add in a gratuitous number of references from different people saying the same thing. The exception to the latter rule is if you're trying to demonstrate the multiplicity of work in an area. For example, if I wanted to say that I was building on the existing chicken theft literature, I might say "(e.g. Jones 1999, Smith 2005, Bloggs 2010)". Otherwise, stick to using them when they're relevant to what you're saying.
4. Quality and quantity both matter
With the above said, the real question we're trying to answer here is how much reading you need to do for an essay.
Obviously there are a few factors at play here. Is it 1000 words, or 1500 words, or 2000 or 2500 words? As the numbers go up, the amount of effort you need to put in to reading for it probably increases. Ditto for how much the essay matters: if it's formative, you probably don't need to worry as much as if it makes up a significant chunk of your final grade.
With that said, let's say that you spend 10 hours reading in order to write a 2500 word essay. How much can you do in that time? You could probably read a couple of books, maybe 10 articles in depth, or you could read 10-20 if you skimmed some and close-read others. In addition, you're probably going to supplement that peer-reviewed material with some newspaper articles and grey literature, especially if you're trying to make a lot of fact-based claims or your essay has contemporary relevance.
I would argue you should prioritise journal articles over book chapters, and book chapters over whole books. The former generally allow you to get a similar feel for an argument, but will take far less of your time and you can cover a lot more ground with them. In addition, prioritise any of the above over newspaper articles. If I see a bibliography which primarily consists of opinion pieces from the Guardian, I can tell the essay is unlikely to be high quality, no matter how much I might like Owen Jones.
So let's say that you find and read 10 journal articles in depth, and you use all of them. Given that all the references are likely to come in the body of your essay, and that takes about 75% of the word count, then you're probably looking at one peer-reviewed reference for roughly every 200 words, based on a 2500 word essay. I'm pretty comfortable with that as a figure, but I'm going to caveat it in the next paragraph.
5. Quality of engagement matters most of all
Honestly, it doesn't matter that much how many authors you cite. What matters is what you do with those references.
What does this mean?
You should be critically engaging with the works that you cite. Rather than just throwing in an author and a date, you should be asking yourself (and then answering in your essay) why that supports the argument that you're making. If you're citing an author so that you can disagree with them, what about their argument do you disagree with? Why? Those few simple questions, if you answer them, will vastly boost the quality of your essay because they'll show that you're thinking about the literature and the subject that you're engaging with, rather than trying to string together an argument and then sprinkling in some citations to make it look "academic".
To sum up:
Make sure you're reading a reasonably broad range of high quality material.
Think about why you're citing someone, and where a citation is necessary (to back up a claim, or to acknowledge where your argument has been preceded by or influenced by another author).
Engage with the material that you're citing.
I hope you found this explainer helpful. If you did, why not check out my other guides on how to write better essays?
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