# How to write a thesis statement

Canonical: https://duckyhelper.com/learn/essay-writing/thesis-statement/
Updated: 2026-10-01

A thesis statement is one or two sentences, usually at the end of your introduction, that state your main claim and the reasons for it. A strong thesis is specific, can be argued against, and gives the reader a map of your essay. It is not a fact, a question, or an announcement like In this essay I will talk about. Test it by asking: could a thoughtful person disagree?

## What a thesis does

Purdue OWL describes a thesis as your main idea or claim, stated in a sentence or two. It is not a title, an announcement of your subject, or a statement of fact. Everything in the essay should support it, so writing it well first makes the rest of the essay easier.

## A simple formula

**Topic + your claim + because (your reasons).** For example: *High schools* (topic) *should start at 8:30 a.m. or later* (claim) *because teenagers who sleep more are healthier and focus better in class* (reasons). The reasons often become your body paragraphs.

## Weak vs strong

| Weak | Strong | Why |
| --- | --- | --- |
| *Many high schools start before 8 a.m.* | *High schools should start at 8:30 a.m. or later because teens need more sleep to stay healthy and focused.* | The weak one is a fact. Nobody can argue with it, so there is nothing to prove. |
| *In this essay, I will talk about social media.* | *Schools should teach students to limit social media at night, because late scrolling cuts into sleep and homework time.* | An announcement names a topic but makes no claim. |
| *Should we protect the oceans?* | *Our state should ban single-use plastic bags, because they make up a large share of the litter on our beaches.* | A question is not a claim. Answer it instead. |
| *Frankenstein is a book with many themes.* | *In Frankenstein, Mary Shelley suggests that the creature turns violent because people reject him, not because he was born evil.* | Too vague. The strong version takes a position a reader could dispute. |

## Worked examples

**Example 1: from topic to thesis**

Problem: Your teacher says: write an argument about cell phones in school.

1. Turn the topic into a question with two sides: *Should phones be allowed during class?*
2. Pick your answer: *No, they should be stored during class.*
3. Add your reasons: *because they distract students and make it easier to cheat on quizzes.*
4. Check: could someone disagree? Yes, some students and parents want phones for emergencies. So it is arguable.

Answer: *Phones should be stored away during class, because they distract students and make it easier to cheat on quizzes.*

**Example 2: narrow a thesis that is too broad**

Problem: *Pollution is bad for the environment.*

1. Who would disagree? Almost no one. That means it is too broad.
2. Narrow the topic: which pollution, where? *Plastic litter in our town's river.*
3. Make a claim about what should happen and why.

Answer: *Our town should add trash traps to the river's storm drains, because most of the plastic in the river washes in from the streets.*

**Example 3: a thesis for a literature essay**

Problem: Prompt: What does the ending of a novel you read reveal about its main character?

1. Avoid plot summary like *At the end, she moves away.* That is a fact from the book.
2. Say what the ending shows and why it matters: an interpretation another reader could challenge.
3. Name the evidence you will use, so the reader can see your map.

Answer: *The novel's ending shows that the narrator's courage comes from her loyalty to her brother, not from fearlessness, as her choices in the final two chapters reveal.*

## Common mistakes and fixes

| Mistake | Fix |
| --- | --- |
| Stating a fact | Ask *so what?* and make a claim about the fact. |
| Announcing the topic (*This essay will discuss*) | Delete the announcement and state your position directly. |
| Being too broad (*Technology changed the world*) | Narrow to one place, group or time: *how phones changed our school's lunch period*. |
| Listing reasons that do not match the body paragraphs | Update the thesis after you draft so it matches what you actually proved. |
| Hiding the thesis in the middle of the introduction | Put it at the end of the introduction, where readers look for it. |

## Practice

**Five thesis questions**

1. Which is the strongest thesis for an essay about school start times?
   A. High schools should start at 8:30 a.m. or later, because teenagers who sleep more are healthier and focus better in class.
   B. In this essay, I will discuss school start times.
   C. Should high schools start later?
   D. Many high schools start before 8 a.m.

   Answer: High schools should start at 8:30 a.m. or later, because teenagers who sleep more are healthier and focus better in class.. It makes a specific, arguable claim and gives reasons. The others break the rules on this page: *Many high schools start before 8 a.m.* is a fact, *In this essay, I will discuss* is an announcement, and *Should high schools start later?* is a question.

2. What is the main problem with this thesis? *The Great Depression was a hard time for many Americans.*
   A. It states something almost no one would dispute, so there is nothing to argue.
   B. It is a question.
   C. It is too long.
   D. It uses the word *I*.

   Answer: It states something almost no one would dispute, so there is nothing to argue.. A thesis must be arguable. This sentence is short, is not a question, and does not use *I*. Its problem is that it is too broad and widely accepted.

3. Which thesis makes an arguable claim about the novel *Frankenstein*?
   A. In *Frankenstein*, Shelley suggests the creature turns violent because people reject him, not because he was born evil.
   B. This essay is about *Frankenstein*.
   C. *Frankenstein* was written by Mary Shelley and published in 1818.
   D. *Frankenstein* is a book with many themes.

   Answer: In *Frankenstein*, Shelley suggests the creature turns violent because people reject him, not because he was born evil.. It is an interpretation another reader could challenge. The publication sentence is a fact, *This essay is about* is an announcement, and *a book with many themes* is too vague to argue for or against.

4. Where does the thesis usually go in a short school essay?
   A. In the first sentence of the conclusion
   B. At the end of the introduction
   C. In the title
   D. In the middle of the second body paragraph

   Answer: At the end of the introduction. Placing the thesis at the end of the introduction tells the reader your claim before the evidence begins. A conclusion restates it, and a title is not a thesis.

5. Which revision turns *Social media is bad* into a specific, arguable thesis?
   A. Social media is very bad for everyone.
   B. Social media has good and bad sides.
   C. What is social media doing to us?
   D. Schools should teach students to put phones away at night, because late-night social media cuts into sleep and homework time.

   Answer: Schools should teach students to put phones away at night, because late-night social media cuts into sleep and homework time.. It names who should act, what they should do, and why, and a reader could disagree. The others stay vague, refuse to take a side, or ask a question.

## Frequently asked questions

### How long should a thesis statement be?

Usually one sentence, sometimes two for a longer essay. Purdue OWL describes it as a main claim expressed in a single sentence or a combination of sentences. If yours runs longer than two sentences, it probably includes evidence that belongs in the body paragraphs.

### Can a thesis have three reasons?

Yes. A three-reason thesis gives the reader a clear map for a five-paragraph essay. But reasons are not required, and longer essays often state a claim without listing every reason. Make sure any reasons you list match your body paragraphs, in the same order.

### Can I change my thesis after I start writing?

Yes, and you often should. Drafting shows you what you can actually prove. When you finish the draft, reread the thesis and revise it so it matches the essay you wrote.

### Can Ducky help with my thesis?

Ducky is built to help you understand, not to do your work, so it will not hand you a thesis to copy. It can ask you questions, check whether your thesis is arguable and specific, and point out where it does not match your paragraphs. See [AI use and academic integrity](https://duckyhelper.com/legal/ai/).

## Sources

- [Purdue OWL, Creating a Thesis Statement, Thesis Statement Tips](https://owl.purdue.edu/owl/general_writing/the_writing_process/thesis_statement_tips.html), accessed 2026-10-01
- [Purdue OWL, Developing Strong Thesis Statements](https://owl.purdue.edu/owl/general_writing/academic_writing/establishing_arguments/index.html), accessed 2026-10-01

## Related

- [How to write an introduction paragraph](https://duckyhelper.com/learn/essay-writing/introduction-paragraph/)
- [How to outline an essay](https://duckyhelper.com/learn/essay-writing/essay-outline/)
- [How to write an argumentative essay](https://duckyhelper.com/learn/essay-writing/argumentative-essay/)
- [Essay Writing study guides](https://duckyhelper.com/learn/essay-writing/)

## Try asking Ducky

- "Read my intro and tell me if my thesis is clear."
- "Is my thesis arguable, or is it just a fact? Ask me questions until I fix it."
- "Does my thesis match what my body paragraphs actually prove?"

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