A PhD dissertation is a substantial project, and it’s important to plan accordingly. The average time to complete a doctoral dissertation is seven years, but this can vary widely depending on the requirements of your university or institution. It’s also important to note that there are no strict deadlines for submitting your thesis; instead, you’ll want to submit your dissertation when you think it’s ready. Depends on the topic. The average dissertation takes about four months, but it’s not unusual for some people to spend longer than that.