The long and short of it: what is the optimal length for a PhD?

​A PhD can feel like a lifetime, or be over in a flash. How long it takes will, in large part, be determined by what country you’re studying in. In North America, it’s common for PhDs to last more than 5 years, whereas in Europe it can be quite rare for them to go for more than 4. System-differences aside, at some point, students are also faced with the decision of when to hand in and defend their thesis. So what is the best programme length, and when should you opt for a quicker submission or a later one? Turns out, there are lots of factors that might influence what decision is best for you.

Written by Damien
​@DamienFarine

Choosing the right programme length for you
 
If you’re on the hunt for a PhD programme, you might have noticed a lot of variation in how long PhDs take. Differences arise between countries or between different types of institutions. For example, it is common for PhDs in some countries to include formal classes during the first few years and /or some teaching requirements. In the USA, a student might spend two years before even formally starting their PhD and have quite open-ended timeframes for completion. By contrast, other countries, such as Germany, the UK or Australia, have few or no classes but can have quite strict finishing timelines­—sometimes as fast as 3 years. Within a country, some institutions have more generous baseline funding, that give PIs some flexibility to extend students, whereas grant-based positions often have very limited opportunities for continuation beyond a fixed end time.
 
If you have the luxury of choice, choosing between options can seem quite daunting. As a rule-of-thumb, you can expect longer programmes to give you more opportunity to explore ideas and provide a more comprehensive continued education. However, if you already have your perfect ideas in place, spending a year or two doing classes can also feel like a major distraction. Thus, there is no one perfect solution, and thinking about your expectations both now and in the future might help you to find what is likely to be best for you.
 
As you navigate different options, you might want to consider the following questions:
 
(1) Are the scientific aims of the project already clearly laid out? Many European-based projects are funded by grants to PIs, and therefore they’ve already had to outline and defend their ideas. In such cases, a student is much more likely to ‘hit the road running’, but they can often also restrict the possibilities for more independent exploration of ideas.
 
(2) What are your future career plans? Believe it or not, some higher-level academic positions have an age limit, so if you’re starting your PhD a bit later and already have some experience (like I did—at 29—and having worked in Science for a few years) then you might veto a lengthier programme. If, instead, you’re straight out of school and undergrad, then having a bit more time to explore ideas might be beneficial. (In these situations, exploring options of working as a field assistant might be a great way to gain more direct research experience without committing to a whole programme).
 
(3) What are the personal and/or financial implications of the programme? Different countries have very different funding models for PhDs. In some countries you are employed as a government employee, whereas in others all PhDs are funded on stipends with no benefits. (This can also vary within a country). If the funding doesn’t cover all of the costs (and even if it doesn’t allow saving), then a shorter programme will help mitigate how far backwards you go financially. It’s also worth considering the extra costs that might come with your decision. For example, living away from family or a partner might have more travel and accommodation expenses (my wife and I have maintained two households for a large part of our research careers so far, which is financially draining). Long-distance relationships might seem more feasible for a shorter rather than longer. Further, some opportunities have guaranteed funding for the entire period, whereas others might require applying for continuation funding (which takes time away from your project and can, paradoxically, delay your completion). Finally, some programmes (often positions funded by grants) will come with funding for going to conferences, but I also met many students who had to fund their own way (this seems to be more common in longer, ‘more independent’ programmes).

Deciding on when to hand in

There are obviously many more factors that might go into individual decisions about what programmes are more suitable, and what length of programme is best. However, the length of the programme is not only decided by the programme itself—we also have a lot of control over this. For example, I submitted my PhD thesis months before my funding ended, and much earlier than the firm deadline set by the university, but this was because a good postdoc opportunity presented itself.
 
As completion of the PhD starts to loom, it is surprisingly common for PhD students to be faced with making decisions on when to hand in. It might seem that the end time should be quite standardised, as most programmes have a relatively fixed funding period or even hard deadlines. But there can also be opportunities to delay submitting, for example through funded extensions. So, should you rush to get it all done, or take your time? As always, the answer to this is going to be very much dependent on personal circumstances.

Wearing a silly hat might seem like a major priority in life, but rushing to submit your thesis might not always be the most strategic option. For me it was driven by an opportunity to move onto a very exciting postdoc, but in the long-run it means that my academic progress is often compared with a cohort that started their PhDs much earlier than I did.

First and foremost, doing a PhD is tough! Extending a Phd might seem like it might help to relieve some of the pressure. But, in reality, pressure comes from factors that are not deadline-related (e.g. writing, procrastination, etc.). So if you are feeling burn-out creeping in after 3 years, it is important to ask whether spending more time in the lab will help or just provide more opportunities to hit your breaking point? A primary consideration should be with mental health (and trust me, while getting Dr. in front of your name might seem like it will make it all worthwhile in the end—it doesn’t).
 
There are, of course, also financial considerations. Many PhD positions are paid substantially less than alternative careers, or than being a postdoc. Spending longer in a PhD programme can put you further behind financially. I find this to be particularly important for those considering leaving academia after their PhDs, as they are really losing out on future earning potential. Often my recommendation in these cases is to finish as fast as possible, as the outputs that might be important for an academic progression (i.e. the number of publications and their impact) will not be weighted as highly when applying for industry positions (and for promotions thereafter).
 
Individual circumstances apart, there might also be some good reasons to delay submitting as long as possible. These are especially true for those hoping to continue along the academic track. For example, many competitive postdoctoral programmes (like fellowships) count productivity based on the number of years since PhD, and almost never consider the time actually taken during the PhD. For example, ERC Starting Grants have a limit of 2–7 years since the completion of a PhD (usually the PhD defense). The date for calculating this is (or at least was for Horizon 2020) the 1st of January in the year that grants are awarded (for example for the 2019 call that I submitted to, with a submission date of 2019, an applicant must have defended/received their PhD after the 1st of January 2012). Thus, delaying the defense from December to January can give a whole extra year of eligibility to this programme. Maybe more importantly, spending more time on a PhD can result in having more outputs to list on your CV, making you (appear) more competitive against other applicants at the ‘same career stage’. This is becoming more and more the case as funding agencies begin evaluating applicants against their cohort (among other considerations of opportunity*) rather than using absolute metrics. An example of this is the Australian Research Council’s Research Opportunity and Performance Evidence (see https://www.arc.gov.au/policies-strategies/policy/arc-research-opportunity-and-performance-evidence-rope-statement).
 
So why not delay forever? Firstly, in many countries it is necessary to have obtained your PhD (or at least have qualified for it, e.g. by having completed the defense) before you can be employed as a postdoc. Second, when applying for postdocs, an important skill to demonstrate is the ability to complete research. Most PIs fund postdocs through grants, and therefore have obligations to deliver to these grants (the same with PhDs, which is usually a good motivator for the PI to support their students). Delays in completing a PhD can be a red flag to a potential supervisor. It can make it look like the person cannot effectively complete research, or at least might make applicant A without their PhD seem like a greater risk than applicant B with their PhD in hand.
 
Finally, a really important consideration is personal development. On the one hand, it could be that there is a major question that still needs to be answered from the PhD. For example, it could be necessary to do some extra work on a major experiment if this will strengthen the resulting publication. (Though consider whether this should be done as a postdoc instead of a PhD). In general, if there is unfinished work to be completed, then delaying submission would not be regarded as wasting future time (i.e. opportunity loss). However, often it is also worth thinking whether it is now time to move on. A PhD—or even a whole lab or university—can often only give one perspective on the world. Changing projects, groups, departments, or institutions can be a very important part of the academic development (see some of my thoughts on this in a previous post).
 
The verdict?
​
When making plans for your PhD—both beforehand, and as you near completion—consider all of the options available to you. It is often important to think about this with a longer time horizon than you might be focused on right now (e.g. getting a PhD, or getting the PhD finished to become a Dr.), because the decisions we make now can have ramifications for the future. Here, it’s important to consider the potential to gain (e.g. by increasing how long you’ll be eligible for grants) and lose (e.g. falling behind financially or advancing more slowly) opportunities based on a decision. Some of this will be determined (at least in part) by what career track you see yourself on (e.g. moving to industry versus trying to continue in academia), by your personal circumstances (relationships and mental health are critical here), and where you want to go next (e.g. what country you’re moving to, or if your scholarship requires a return phase that will take time away from future postdoc opportunities).

*It is now generally the case that the timings in the eligibility criteria for fellowships and grants include extensions for career breaks. For example, many give an extra year to the eligibility for every child. Some are more equal (providing similar extensions to both fathers and mothers), and others aren’t quite there yet. It might also be worth considering your options if you are planning on starting a family.