How to Write an Annotated Bibliography (With Examples)

TL;DR

• An annotated bibliography is a list of sources (like a Works Cited page) where each source has a short paragraph evaluating and summarizing it
• Each annotation is typically 100-200 words and covers what the source says, how credible it is, and how it relates to your research
• There are two main types: descriptive (summarizes) and evaluative (summarizes AND judges quality/usefulness)
• Most professors want evaluative annotations — check your rubric to be sure

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You check your assignment sheet and see "annotated bibliography" and think: "Is that just a bibliography... with notes?"

Basically, yes. But the "notes" part is where students get tripped up. How long should each annotation be? What goes in it? Do you just summarize the source or do you need to say more?

Let's clear this up once and for all.

What Is an Annotated Bibliography?

An annotated bibliography has two parts for each source:

1. The citation — formatted in whatever style your professor requires (APA, MLA, Chicago)
2. The annotation — a short paragraph (usually 100-200 words) that summarizes the source and evaluates its relevance to your research

That's it. It's a research tool that shows your professor you've actually read and thought about your sources, not just Googled them and slapped them into a Works Cited page.

Why Professors Assign Them

They're checking that you can:

• Find credible, relevant sources
• Actually read and understand those sources
• Evaluate whether a source is trustworthy and useful
• Connect multiple sources to a research topic
• Think critically about information (not just accept it at face value)

Annotated bibliographies are often assigned as a step toward a larger research paper. Your professor wants to see your research progress before you write the full paper.

Two Types: Descriptive vs. Evaluative

Descriptive (Summary) Annotations

These just summarize the source. What does the author argue? What evidence do they use? What are the main findings?

When to use: When your professor just asks you to "summarize your sources."

Evaluative (Critical) Annotations

These summarize AND assess. Is the source credible? What are its strengths and limitations? How does it fit your research? Is the methodology sound?

When to use: When the assignment says "evaluate," "analyze," or "assess" your sources (this is more common).

When in doubt: Write evaluative annotations. They show more critical thinking, and professors generally prefer them.

How to Write Each Annotation: A 4-Step Formula

For each source, cover these four things in roughly this order:

Step 1: Summarize (2-3 sentences)

What is this source about? What's the author's main argument or finding?

"This study examined the effects of sleep deprivation on academic performance among undergraduate students. Through a survey of 500 participants, the researchers found that students who slept fewer than six hours per night had GPAs an average of 0.4 points lower than those who slept seven or more hours."

Step 2: Evaluate (1-2 sentences)

Is this source credible? What are its strengths or weaknesses?

"The study's large sample size strengthens its findings, though the reliance on self-reported sleep data introduces potential bias. The research was published in the peer-reviewed Journal of College Student Development, adding to its credibility."

Step 3: Reflect on Relevance (1-2 sentences)

How does this source relate to YOUR research question?

"This source directly supports my thesis that universities should implement later class start times. The quantitative data on GPA differences provides concrete evidence for the academic consequences of sleep deprivation."

Step 4: Connect (Optional, 1 sentence)

How does this source relate to your OTHER sources?

"Unlike Martinez (2023), who focused on high school students, this study's college-specific data is particularly relevant to my research scope."

Full Examples

APA Format — Evaluative Annotation

Walker, M. P. (2019). The sleep-deprived student: Links between sleep, health, and academic performance. Journal of College Student Development, 60(4), 431-448. https://doi.org/10.xxxx/xxxx

Walker examined the relationship between sleep patterns and academic outcomes in a longitudinal study of 1,200 first-year college students over two semesters. The study found a significant correlation between consistent sleep schedules (not just total hours) and higher GPAs, with the strongest effects observed in STEM courses requiring problem-solving. The longitudinal design and large sample are notable strengths, though the study was conducted at a single large public university, which may limit its generalizability to smaller institutions or community colleges. This source is central to my research on sleep and academic performance because it identifies sleep consistency — not just duration — as a key variable, which adds nuance to my argument. Walker's findings complement those of Alhola and Polo-Kantola (2007), who focused more broadly on cognitive impairment from sleep loss.

MLA Format — Evaluative Annotation

Walker, Matthew P. "The Sleep-Deprived Student: Links Between Sleep, Health, and Academic Performance." Journal of College Student Development, vol. 60, no. 4, 2019, pp. 431-448.

This longitudinal study tracked 1,200 first-year college students across two semesters to examine how sleep patterns affect grades. Walker's key finding was that consistent sleep schedules mattered more than total hours slept, with the strongest GPA impact in problem-solving-heavy courses like math and engineering. The study's scope and duration make it a strong source, though its limitation to one large public university means the results might not apply to all college settings. For my research paper on whether universities should adjust scheduling to support student sleep, this article provides essential data showing that the issue goes beyond simply telling students to "sleep more" — institutional factors like class timing play a role. This source works well alongside broader cognitive research by other sleep scientists.

APA Format — Descriptive Annotation

National Sleep Foundation. (2024). Sleep in America: College student report. https://www.sleepfoundation.org/professionals/sleep-america-polls

This annual report from the National Sleep Foundation surveyed 2,000 college students about their sleep habits, challenges, and perceptions. Key findings include that 73% of students reported inconsistent sleep schedules during the academic year, and 62% said academic stress was the primary barrier to better sleep. The report also documents the prevalence of caffeine use and napping as compensatory strategies. As an industry report from a major sleep advocacy organization, it provides useful descriptive statistics, though it lacks the methodological rigor of peer-reviewed research. The survey data contextualizes the broader sleep crisis on college campuses and provides compelling statistics for the introduction of my paper.

Common Mistakes to Avoid

Mistake 1: Writing a Book Report

Your annotation isn't a detailed summary of everything in the source. Hit the main argument and key findings in 2-3 sentences, then move on to evaluation and relevance. If your summary is longer than your analysis, you're off balance.

Mistake 2: Only Summarizing (When They Want Evaluation)

"This article discusses the effects of social media on teenagers" — that's descriptive. Your professor probably wants: "While this article provides useful survey data, its sample of only 50 participants from one school limits generalizability. The findings about screen time and anxiety align with my thesis and complement larger studies by Twenge (2021)."

Mistake 3: Not Connecting to Your Research

Every annotation should explain why you chose this source and how it relates to your specific topic. "This is a useful source" isn't enough. Say WHY it's useful.

Mistake 4: Using Only One Type of Source

Professors want to see variety: peer-reviewed journal articles, books, reports, and maybe reputable news sources or government data. Five sources from the same journal looks lazy.

Mistake 5: Not Actually Reading the Source

Your professor can tell when you've only read the abstract. If your annotation could have been written from the abstract alone, you haven't gone deep enough. Read at least the introduction, results, and discussion of journal articles.

Mistake 6: Getting the Citation Format Wrong

This is pure points lost for no reason. Double-check your citations against the official APA or MLA guidelines. Pay attention to:

• Italics (journal names, book titles)
• Capitalization (APA uses sentence case for article titles)
• DOIs and URLs
• Hanging indents
• Punctuation (every period, comma, and colon matters)

How Many Sources Do You Need?

This varies wildly by assignment, but here are rough guidelines:

• Freshman composition: 5-8 sources
• Upper-division research paper: 10-15 sources
• Graduate level: 15-25+ sources
• Your specific assignment: Check. Your. Rubric.

When choosing sources, aim for:

• Mostly peer-reviewed journal articles (these carry the most weight)
• A few books or book chapters from experts in the field
• Government or organizational reports for statistics
• Maybe 1-2 reputable news sources for current context
• Zero Wikipedia, zero random blogs (use them for leads, not as citations)

Finding Good Sources

Your library database is your best friend. Most students go straight to Google, but academic databases give you:

• Peer-reviewed articles (the gold standard)
• Full-text access (already paid for by your tuition)
• Better search filters (date, subject, methodology)

Best databases for most subjects:

• JSTOR (humanities and social sciences)
• PubMed (health, biology, medicine)
• IEEE Xplore (engineering, computer science)
• PsycINFO (psychology)
• Google Scholar (cross-disciplinary, but filter carefully)

Search Tips

• Use Boolean operators: "sleep deprivation" AND "academic performance" AND "college students"
• Filter by date to get recent research (last 5-10 years)
• Check the reference lists of good articles to find more sources (the "snowball" method)
• If you find a great article, search for papers that cite it to find newer related work

A Time-Saving Workflow

Here's how to do an annotated bibliography efficiently:

1. Find all your sources first (don't annotate one by one). Do a research session, download/bookmark everything promising.
2. Skim each source — read the abstract, introduction, and conclusion. Star the ones that are actually relevant.
3. Read the best sources more carefully — take notes as you read.
4. Write all citations first — get the formatting done in one batch.
5. Write all annotations — now you can see patterns across your sources and write about connections.

This batching approach is way faster than the stop-and-start method of finding one source, reading it completely, writing the annotation, then finding the next one.

If you're struggling to understand a complex source — like a dense journal article with heavy statistics — Gradily can help you break down the key arguments and methodology so you can write a more informed annotation.

Formatting Quick Reference

APA 7th Edition

• Double-spaced throughout
• Hanging indent for citations (0.5 inch)
• Annotation starts on the line after the citation, indented 0.5 inch
• 12pt Times New Roman
• No bold or italics in annotations (only in citations where required)
• Alphabetical order by author's last name

MLA 9th Edition

• Double-spaced throughout
• Hanging indent for citations (0.5 inch)
• Annotation starts on the line after the citation, indented 0.5 inch
• 12pt Times New Roman
• Alphabetical order by author's last name
• Title: "Annotated Bibliography" centered at top

Chicago/Turabian

• Same general format but uses footnote-style citations
• Check with your professor — Chicago has two systems (Notes-Bibliography and Author-Date)

The Bottom Line

An annotated bibliography is honestly one of the more straightforward assignments you'll get in college — once you understand the format. The hard part isn't the writing; it's the research.

Find good sources, actually read them, and then write a focused paragraph for each one that shows you understand what you read and why it matters for your project.

If you can do that, you're golden. And if the research process itself is confusing — figuring out databases, evaluating sources, understanding dense academic writing — Gradily is built to help with exactly that kind of thing. Ask it to explain a confusing concept from a journal article, and suddenly your annotation writes itself because you actually get what the source is saying.

Now go build that bibliography.