How Long Does a PhD Take? What the National Data Shows

For a research doctorate in the United States, the median recipient took 8.6 years from a bachelor’s degree, 7.0 years from starting graduate school, and 5.8 years from starting the doctoral program. Those are three different clocks, and mixing them is the main reason estimates for how long a PhD takes seem to disagree.

The federal Survey of Earned Doctorates for 2025 reports those medians for all fields. In this guide, “PhD” means a research doctorate. The numbers are medians; they describe how long recipients took, not how long you will take.

What are the three clocks for a PhD?

The first clock starts at the bachelor’s degree. It includes any time between college and graduate school: a master’s, a job, a gap year, a post-bacc, or a period when you were applying. That is why the from-bachelor’s number is the largest.

The second clock starts when you begin graduate school. If you enter a master’s program first and then continue to a doctorate, this clock includes the master’s. If you enter a doctoral program directly, this clock and the doctoral-program clock may start at the same point.

The third clock starts when you begin the doctoral program itself. This is the closest number to “the PhD” as most people picture it. It measures the doctoral program, not the full path to it.

These are elapsed-time medians, not a measure of weekly hours or funding. Funding can also run on a different clock from the degree. A funded studentship may end before the thesis is submitted, and a fellowship may cover fewer years than the degree takes. That difference matters when you compare offers or plan how long you can stay enrolled.

How long does a PhD take in different fields?

The broad-field medians show differences by field. The clock still changes what the number means. Here are the medians from the same survey.

Science and engineering: 8.0 years from a bachelor’s degree, 6.8 years from starting graduate school, 5.7 years from starting the doctoral program.
Biological and biomedical sciences: 8.0 years from a bachelor’s degree, 6.3 years from starting graduate school, 5.7 years from starting the doctoral program.
Physical sciences: 6.8 years from a bachelor’s degree, 6.0 years from starting graduate school, 5.8 years from starting the doctoral program.
Geosciences, atmospheric, and ocean sciences: 7.8 years from a bachelor’s degree, 6.4 years from starting graduate school, 5.7 years from starting the doctoral program.
Computer and information sciences: 8.1 years from a bachelor’s degree, 7.0 years from starting graduate school, 5.6 years from starting the doctoral program.
Engineering: 7.4 years from a bachelor’s degree, 6.4 years from starting graduate school, 5.3 years from starting the doctoral program.
Mathematics and statistics: 7.0 years from a bachelor’s degree, 6.1 years from starting graduate school, 5.6 years from starting the doctoral program.
Health sciences: 11.0 years from a bachelor’s degree, 8.7 years from starting graduate school, 5.0 years from starting the doctoral program.
Agricultural sciences and natural resources: 8.6 years from a bachelor’s degree, 7.0 years from starting graduate school, 5.0 years from starting the doctoral program.

The from-bachelor’s number can be much longer than the doctoral-program number because it includes earlier study and time away from school. Health sciences shows that clearly: the median from a bachelor’s degree is 11.0 years, while the median from starting the doctoral program is 5.0 years. That gap does not mean the PhD itself takes eleven years. It means the full path from a bachelor’s degree did, for the median recipient in that group.

What makes a PhD take longer?

These are medians, not reasons. But the general reasons are not mysterious. A PhD is a research apprenticeship with milestones, and delays usually come from the parts that depend on other people, equipment, access, or life circumstances.

Things that stretch a PhD include switching advisors or labs, changing projects after a failed experiment or a shift in funding, waiting for equipment or data access, and completing extra coursework or teaching duties. Fieldwork can be delayed by weather, permits, or travel. Lab work can be delayed by materials, space, or a protocol that does not work. Writing and revision can take longer than expected, especially when a committee needs to be assembled and read a full draft.

Part-time study stretches the calendar. So do funding gaps. Personal circumstances—health, family care, visa rules, or a move—can also add time. These are the ordinary reasons elapsed time grows.

What about PhD funding length in the UK?

In the UK, UKRI says funding for full-time studentships usually lasts between three and four years. That is a funding length, separate from time to thesis submission. The material used here does not give a UK median completion time, so there is no UK median to quote alongside the US figures.

If you are comparing countries, keep the clocks separate: funding length, program length, and time to thesis submission are not the same measure. Ask what the funding covers, including a writing-up period, and what happens if you need more time.

What to do next

Decide which clock you need. If an employer or program asks for “time to degree,” ask whether it means from bachelor’s, from graduate school, or from the doctoral program.
Ask programs for their time-to-degree data and funding length in writing. Compare the funding period with the program’s typical completion time, not with the full from-bachelor’s figure.
Check what happens when funding ends: tuition, health insurance, teaching, and a writing-up period. Get the answer before you accept an offer.
If you are choosing between routes, use do you need a PhD to be a scientist?, PhD vs. master's, and academia vs. industry to frame the decision. For the wider career path, see how to become a scientist.