A Master’s dissertation can range from 12 thousand to 20 thousand words while a Ph.D. dissertation can go up to 80 thousand words depending on many factors.  It can take you 2 to 18 months to finish a Ph.D. dissertation. The time taken to finish a dissertation depends on the nature of your topic and research. How dedicated you are towards your dissertation as well as your interest in the research. If you dedicate yourself and keep up with the schedule that you have made for your dissertation then you can easily finish your dissertation in 2 months or so.