How Many Sources Does a Research Paper Need?

Instructors ask for a number of sources because a research paper is supposed to rest on evidence, not on one book or a handful of websites. But no style guide or university sets a universal count. Librarians at the University of California, Santa Barbara put it plainly for literature reviews: there is no magic number, and how many sources you need depends on the topic and the type of review (UCSB Library). So start with the assignment, then use the rule of thumb below to sanity-check your plan.

How many sources for a 3, 5, 10, 15, 20 or 30-page paper?

The table is a rule of thumb we use for planning, not a rule any institution publishes. It assumes scholarly sources (journal articles, academic books) that you actually cite in the text, and a double-spaced page of about 300 words in 12-point Times New Roman (our measurement, see the words to pages converter).

Read the ranges like this: the low end is enough for a paper that analyzes a few sources closely (a history paper built on primary documents, for example); the high end fits a paper that surveys a field, such as a literature review. When the assignment gives a minimum, treat it as a floor, not a target.

What if the assignment gives a word count instead of pages?

Convert it first: at about 300 words per double-spaced page, a 2,000-word paper is close to 7 pages and a 4,000-word paper about 13. Then read the table at the nearest page count. For example, a 2,500-word undergraduate paper (about 8 pages) lands between the 5-page and 10-page rows, so 6 to 10 cited sources is a sensible plan. Short reflective or argumentative pieces need fewer sources than their length suggests; literature reviews need more.

What does your assignment actually ask for?

Before counting, check what kind of sources the instructor wants, because "five sources" rarely means any five. Look for these words on the assignment sheet or rubric:

• Scholarly or peer-reviewed: articles written by experts for other experts, usually in academic journals. Cornell University Library describes scholarly articles as written by scholars or professionals who are experts in their fields, who in the sciences and social sciences often publish research results (Cornell University Library).
• Primary sources: firsthand material such as letters, speeches, data or original studies (see primary vs secondary sources).
• Recent: a date limit such as "published in the last ten years."
• Excluded types: many instructors exclude encyclopedias, general websites or textbooks as cited sources.

If the sheet says nothing, ask. A one-line email ("Should my sources be peer-reviewed, and is there a minimum?") saves you from rewriting.

What counts as a source?

A source counts when you cite it in the text and list it in your references or works cited. Background reading you never cite doesn't count, and neither does listing the same work twice. As a guide:

Encyclopedias and textbooks are still useful for orientation and for finding the scholarly works they cite; they just make weak evidence in a college paper.

How many sources should you find before you start writing?

More than you will use. The University of the District of Columbia library suggests a simple guideline: multiply the number of required sources by three, so if you need 10 sources, find 30 (UDC Library). You won't cite all of them, but you'll understand the topic better and can keep only the strongest.

A practical way to cut the pile:

1. Skim each abstract and conclusion. Drop sources that don't speak to your research question.
2. Keep sources that disagree with each other; disagreement gives your paper something to analyze.
3. Prefer sources that report evidence (data, documents, studies) over sources that only summarize others.
4. Check the reference lists of your best sources for the works everyone cites. Those are usually the ones your instructor expects to see.

Where to look in the first place: how to find scholarly sources.

How recent should your sources be?

It depends on the field and the topic. The CRAAP test from California State University, Chico starts with currency and asks, among other questions, whether your topic requires current information or whether older sources will work as well (Meriam Library, CSU Chico). The University of Kansas writing center makes the same point: for some projects, documents published decades ago are still valuable or even essential, but if your subject is current, your information should be current (KU Writing Center).

A good test: if a newer study exists that updates or overturns an older one, cite the newer one (and the older one too, if you discuss the change).

How many citations should be on each page?

There is no per-page quota. The rule is to cite every time you use someone else's idea, data or words. The St. Francis College library says there is no magic number of in-text citations; each time you use an idea or words from someone else you should provide a citation, which can mean several citations in one sentence or one at the end of a paragraph (St. Francis College Library).

In practice, most body paragraphs of a research paper contain at least one citation, because each paragraph makes a claim and backs it with evidence. Paragraphs of pure analysis, and your introduction and conclusion, may have fewer. If you write a whole page without a single citation, check whether you are still using evidence or have drifted into opinion. For the exact format of each citation, see APA 7 citation examples.

Is it better to have more sources or better sources?

Better. A paper with eight strong, well-used sources beats one with twenty that each appear once in a list. Signs that you have too many sources and too little analysis:

• Each paragraph strings together three or four quotations with no explanation in between.
• Several sources make the same point and you cite them all for it.
• You cite a source only for a general fact that any textbook states.

Signs you have too few:

• One source supplies most of your evidence.
• Every source takes the same side, so the paper has no counterargument.
• You can't support a key claim except with your own assertion.

Rule-of-thumb checklist

• The assignment's minimum is met, with the right kinds of sources (scholarly, primary, recent).
• Every source on the reference list is cited in the text at least once, and vice versa.
• No single source carries most of the paper.
• You include at least one source that disagrees with your thesis, and you answer it.
• Recent research is included wherever the topic changes quickly.

For how the sources fit into the whole writing process, see how to write a research paper.