Thesis vs Dissertation: Key Differences Explained

In the United States, a thesis is a research project completed for a master's degree, and a dissertation is the original research document completed to earn a doctoral degree (PhD, EdD, or similar). The two terms refer to different documents at different levels of education, with different requirements and purposes.

This distinction is commonly misunderstood because the words are sometimes used interchangeably in casual conversation, and because in the United Kingdom, Australia, and many European countries the terms are used in the opposite way.

The Core Difference

The most important difference is the type of research required. A master's thesis demonstrates that you can engage with existing scholarship, analyze it critically, and draw well-supported conclusions. A doctoral dissertation requires you to produce original research that no one else has done, generating new data, new theoretical frameworks, or new interpretations that advance your field.

What a Master's Thesis Involves

A master's thesis is the capstone project for many academic master's degrees. Not all master's programs require a thesis; some programs offer a non-thesis track that substitutes coursework or a comprehensive exam.

When a thesis is required, it typically involves:

• A focused research question that builds on existing literature but does not necessarily produce new primary data
• A literature review that surveys scholarship on the topic
• An argument or analysis that uses existing research to make a claim
• A defense before a committee, which may be required or optional depending on the program

The thesis demonstrates mastery of a subject and the ability to engage in scholarly argument. It is an important academic credential but is evaluated against the standard of graduate-level scholarship, not the original-contribution standard of a dissertation.

What a Doctoral Dissertation Involves

A doctoral dissertation is the primary product of PhD-level study. It is evaluated against the standard of publishable academic scholarship and must represent a genuine contribution to the field.

A dissertation typically requires:

• Original primary research: collecting new data, running new experiments, analyzing original archives, or developing new theoretical frameworks
• A complete dissertation proposal (also called a prospectus), usually defended before a committee before data collection begins
• Multiple chapters: commonly an introduction, literature review, methodology, findings or analysis, discussion, and conclusion
• A formal defense (the PhD dissertation defense) before a committee that may ask probing questions about methods, findings, and implications
• Potential for publication: many dissertations are eventually converted into journal articles or books; committees evaluate whether the work meets publication-quality standards

For a detailed guide to writing one, see how to write a PhD dissertation.

How Terminology Differs Outside the United States

If you are applying to graduate programs internationally or reading scholarship from outside the US, note that the terminology is often reversed:

In the UK, for example, a PhD student submits and defends a "thesis," not a "dissertation." An American reading "PhD thesis" in a British context should understand it refers to the same document Americans would call a "dissertation."

This inconsistency is why the terms are often confused. When reading academic materials or reviewing graduate program requirements, check the institution's specific terminology rather than assuming US conventions apply.

Structural Differences

Beyond the research requirements, a thesis and a dissertation typically differ structurally:

A master's thesis often has:

• Introduction and problem statement
• Literature review
• Methodology (which may use existing data, secondary analysis, or a small original study)
• Results or analysis
• Conclusion

A doctoral dissertation typically adds:

• A more extensive literature review that maps the entire field
• A longer methodology chapter that justifies every design choice
• Multiple results or analysis chapters (sometimes 3 to 4 chapters of findings)
• A detailed discussion chapter connecting findings to existing literature
• Implications, limitations, and directions for future research

The dissertation is longer not because of a page minimum, but because the scope of original research and the requirement to situate findings within the full literature of the field demands more space.

Which Is Harder: Thesis or Dissertation?

A doctoral dissertation is significantly more demanding than a master's thesis, for several reasons:

1. The research standard is higher: Dissertations require original contributions; theses do not.
2. The time investment is longer: A dissertation takes 3 to 7+ years including all doctoral coursework; a thesis typically takes 1 to 2 years.
3. The independence required is greater: After completing coursework and advancing to candidacy, dissertation students define their own research agenda with limited structured guidance.
4. The psychological demands are greater: PhD students experience anxiety and depression at rates significantly higher than the general population, partly because dissertation writing is inherently isolated and ambiguous.

This does not mean a master's thesis is easy. In fields like mathematics or economics, a rigorous master's thesis may represent more intellectual work than a dissertation in a less demanding program. Difficulty is relative to field, institution, and individual program standards.

Does Every Graduate Degree Require One?

Not all master's programs require a thesis. Many programs offer two tracks:

• Thesis track: Complete a research thesis, typically required for students intending to pursue doctoral study or research careers
• Non-thesis track (or coursework track): Complete additional courses, a comprehensive exam, or a capstone project instead of a thesis

Most doctoral programs require a dissertation. Professional doctorates (MD, JD, DDS) typically do not require research dissertations. Some professional doctorate programs (EdD, DrPH) may require dissertations, doctoral projects, or portfolio-based capstones that vary in their research demands from traditional PhD dissertations.

Frequently Asked Questions

Is a PhD a dissertation or a thesis? In the United States, a PhD student produces a dissertation. In the United Kingdom and many Commonwealth countries, a PhD student produces a thesis. The document is the same kind of original research document; the terminology depends on the country's academic conventions.

What is the difference between a dissertation and a thesis? In the US, a thesis is written for a master's degree and focuses on analyzing existing research, while a dissertation is written for a doctoral degree and requires producing original new research. A dissertation is longer, requires a more extensive committee, and is evaluated against the standard of publishable academic scholarship.

Which is harder, a thesis or a dissertation? A doctoral dissertation is significantly harder and more time-consuming than a master's thesis. Dissertations require original research, take years to complete, demand greater intellectual independence, and are evaluated by a larger committee against publication standards. Master's theses are demanding but do not require original contributions in the same way.

How long is a dissertation vs a thesis? A master's thesis in the US is typically 40 to 100 pages (15,000 to 40,000 words). A doctoral dissertation is typically 150 to 400+ pages (60,000 to 100,000+ words), with variation by field. Humanities dissertations tend to be longer; STEM dissertations may be shorter but denser with data and technical content.

Can you get a PhD without writing a dissertation? Most traditional PhD programs require a dissertation. Some programs and institutions offer alternative doctoral credentials (professional doctorates, practice-based doctorates) that substitute a project, portfolio, or practice-based capstone for a research dissertation. These vary significantly in format and requirements.

For guides on writing the documents these programs require, see how to write a PhD dissertation, how to write a literature review, and how to write an abstract.