A doctorate is the highest form of degree -- called a terminal degree -- that educational institutions award. Students usually enter a doctoral program after earning a master’s degree. Doctorates come in two varieties: professional, such as the Juris Doctor or J.D., and academic, such as the Doctor of Philosophy or Ph.D. Most schools estimate that it takes between three and six years of post-master’s-degree work to earn a doctorate, although some students need more time.

Academic Doctorates

Some individual programs give their own estimates that differ from the three-to-six-year standard. The University of California at Berkeley, for example, offers Ph.D. programs in history that have an expected completion of seven years. However, according to a study by the National Science Foundation, students take, on average, 8.2 years to earn a Ph.D. This lengthening is often not due to coursework requirements but to the necessity of completing and defending a dissertation, which is an arduous process.

Professional Doctorates

Students in professional doctoral programs often must complete residencies or practicums before they can practice in their fields, which lengthens the overall time between starting a doctoral program and entering the workforce. A medical student, for instance, completes four years of medical school before graduating with an M.D., but she cannot practice medicine until completing a further three to seven years of residency. A J.D. or professional law degree, takes a full-time student three years to complete, but she then must study for and pass the bar exam in the state where she plans to practice law.

Full or Part Time

Some, but not all, doctoral programs offer students the choice between studying on a full-time or part-time basis. While full-time students take a full course load each semester, part-time students usually enroll in half or fewer credits, which adds two or more years to a student's overall time spent in a doctoral program. Spending more time in a program may seem undesirable, but students choose this option for many sound reasons: They already have careers to attend to, for example, or they don’t want to struggle to achieve good grades.

Picking up a Master’s Along the Way

Some students enter combined master’s and doctoral programs to shave off some of the overall time they will spend in postgraduate study. In these programs, earning a doctorate is the overall goal, but the student is awarded a master’s degree after completing an amount of coursework predetermined by the school. Students usually need about four to five years to complete a doctoral program with a master’s en route, which is about the average for a doctoral program; however, students don’t have to put two years into a master’s program beforehand, which means the total study time is shortened.