PhD Courses that start in January and/or Less than 3 years program
Agree completely with Tree of Life. The other thing to consider is that the final elements of a PhD, which occur after you have written your study can take some time. Eg, even if you believe all is well and you have done all you can or need to do, before submission you have to be signed off and this process can take some time. In my case it will easily be a month all up for this to occur. Then on top of that once you have submitted you have an average of 6-8 weeks before your examiners will complete their reports (this time is quite quick, sometimes they can take longer). You may have a viva or defence presentation to make either before (in my university it is a presentation prior to submission) in UK universities, I think you have a viva or defence afterwards.
Once the examiners have compiled their reports, you then have to do corrections. Not many people have their thesis or dissertation returned without corrections (even minor ones). You are given from between 1 to 6 months to complete corrections (depending on how extensive they are). Once you have made these corrections to the satisfaction of your panel, chair or examiners (it depends on the type of corrections as to who approves them), then your university will confer the award and slot you in to the nearest grad ceremony to confer your degree. So this process also takes some time.
The reality is even if you wrote a thesis in just over two years (which would be a real push but possibly doable if you were not using much new data but were doing a type of review of existing materials), the rest of the process would take you to at least 2.75 to 3 years anyway and, in many cases as Tree as indicated, closer to 3.5 to 4 years all up.
