This is going to be a rather wordy post, and is more directed at those that want to learn more about lightweight backpacking theory and implementation. In the future, I am going to post lots of pictures of several of my updated backpack systems to give the readers a more concrete idea of what exactly it is I am writing about. For now, the focus will be more abstract, and as such, I feel pictures may take away from this post. If you are already schooled in lightweight backpacking or need to have pictures to read long blog posts, you may want to move on.
You have been warned, wall-o-text to follow!
If you have been following my blog, or if you are a backpacker, you already know about lightweight backpacking and what the different terms mean. But for those that might not know, let me explain again.
The goal of the lightweight backpacker is to get under a certain weight in order to have less to carry while out hiking. The weight guidelines are arbitrary of course, but a useful tool in achieving the goal of going lightweight. Why go lightweight? Hauling around a heavy load on your back is exhausting, and the energy you spend on this weight can take away from other goals and activities of the avid backpacker/camper. For example, two people of the same physical condition, height, weight, etc. with two different backpacks will have a finite amount of kilometers they can hike, but the one with the lighter load will be able (all things being equal) to go further.
Now, perhaps walking a long distance through the woods it not a goal of yours (it is for me, I should add). There are other things to consider. What if you want to go swimming? Or fishing? Or harvest wild food like berries and mushrooms? These are all things I enjoy, and these things take time and energy. Even when I don't hike that far, I still want to have the time and energy to devote to fun things other than hiking and carrying a heavy pack. Then there is the issue of wear and tear on your body. The less you strain your joints, for example, with a heavy load, the better off your joints will be in the long term.
However if you are not hiking very far, and don't intend on doing devoting much time and energy to other things (perhaps you just want to set up camp, and sit comfortably by a fire, which is fine) then lightweight backpacking is not for you. Just throw as much gear as you want in your car and in a huge backpack, and have fun at the edges of the woods. You must accept the limitations inherent in this style of camping, however, and because the edges of the woods are easier to get to, don't be surprised when you find say, a loud group of drunken teenagers there too to keep you company.
But for those of us that want to go deeper into the woods, be able to see and do more, and avoid the crowds at the edges, then lightweight backpacking is a logical and very worthwhile endeavor. Lightweight backpacking was pioneered and made more popular largely in the USA, so unfortunately for those of us that prefer the consistent and more logical metric system, the weight guidelines for the different types of lightweight backpacking are defined using pounds. Lightweight (LW) is under 20lbs (about 9kg), Ultralight is under 10lbs (4.5kg), and Super-Ultralight is under 5lbs (2.27kg). These weights refer to base weight, which means all gear without food, water, or fuel--those consumable items always change.
I feel like I have had to explain the above guidelines about a million times in the past year since I have been getting more and more into lightweight backpacking, which tells me that this sub-type of camping is still at least somewhat obscure and less accessible. But don't let this, or the weight guidelines, intimidate you if you are new to camping/backpacking! After reading up a few texts (like this one!), maybe watching a few videos, and doing a bit of research on gear, LW and even UL are relatively easy to get into and accomplish if you have an open mind. SUL is more challenging, I must admit, so be prepared for a challenge there--you will have to give thought to every little gram, and it is only for the more devoted backpacker and not the novice camper.
I have to say that for me one of the biggest challenges was making the jump from traditional (over 20lbs) to LW. I was so set in my ways after about a decade and a half of backpacking/camping, it was hard to change. I love a good challenge, however, and as a skeptic, I also believe it is very important to question everything, even things you already think you have all figured out. There is always room for improvement, and change can be a positive thing, provided that a change is not made in "bad faith", but let's not digress and get all existential.
Once I went LW, going UL was easy, fun, and made a huge overall improvement to my experience in the woods. Another possible hindrance that ought to be noted is price. It is true that quite a lot of specialized UL and SUL gear can come with a big price tag on it, but there are many good, cheap alternatives (some of which I have documented on my blog already, and there will be more to come), especially if you are inclined to DIY/MYOG projects. Going SUL took more planning and thought, but it was also fun, and under certain circumstances also makes a significant improvement to time and energy spent outdoors.
All this begs the question I pose in the title of when to go under the weight guidelines in question. A disclaimer before I attempt to answer said question: I give no objective, 100% accurate formula on how to figure out what system of backpacking is right for all situations and all people. This is obviously a very subjective thing we are dealing with, with virtually an infinite number of variables. All I can give you are answers based on my experiences, and hopefully they will be helpful to you.
I started to get into lightweight backpacking last year, and out of around 20 camping trips I took, I would say half of them were LW and perhaps a few were UL. I have gone camping 14 times this year, and the majority of them have been UL. For me, UL is my go-to system of choice, with LW and SUL being good options should less likely variables present themselves. Due to being a full-time university student, a new father, and other family obligations, I am only able to go on 1-3 day trips. Shorter trips usually facilitate a more lightweight set of gear. Yet even among lightweight backpackers that are able to go on longer, more involved hikes that take weeks or even months and cover hundreds or even thousands of kilometers, there is a debate as to which method is best. What is not as hot a topic, however, is that SUL requires more knowledge and experience from the backpacker, and SUL remains on the fringes of the community (though it is quite a significant fringe group).
For me, a big factor in determining how light to go is the temperature and weather outside. In the winter and late fall/early spring when it can be quite cold, I go generally go LW, as things that keep you warmer tend to weigh more. Thicker sleeping bags, sleeping mats, and clothing need to be added to keep warm. This added weight also has and effect on what kind of backpack to take, because generally the lower weight a backpack is, the less volume and weight allowance it has. So heavier and bulkier gear means a heavier/bigger backpack.
That being said, there are people that are able to go UL in colder temperatures, but I have yet to read a trip report of anyone going SUL in colder temperatures (I am sure that some crazy person out there has done it, though).
Then there is rain. If there is a high chance of rain, rain gear is a good thing to have. There are some lighter options of rain gear than others, but in the end it will still put a dent in your weight allowance even if it is a fancy poncho/tarp or the most high-tech and expensive rain jacket on the market. If you are going on a longer trip, then you simply have to bring rain gear, because we can only predict the weather so far in advance, and even still weather reports are wrong about tomorrow's weather.
So an ideal situation to go SUL is in warm weather with little to no chance of rain. If you live in a warmer, dryer place, then it will perhaps be easier to go SUL. Don't let rain stress you too much--all my gear set ups, be it LW, UL, or SUL, always have some kind of rain gear. So no matter how low you go with weight there are solutions for dealing with rain, and you may be surprised how effective a cheap plastic poncho is at only around 50g.
Another factor is what you want to do outdoors. If you only want to hike/explore, then going UL or SUL is more for you. If you want to do things other than hike, however, then you will probably want to take more things with you. Say you want to go fishing, that will also put a dent in your weight totals, even with the most basic of fishing gear. Or like several friends of mine that have gone camping with me, perhaps you are into photography, and this can put a pretty sizable chunk of weight into your bag.
Depending on how devoted you are to these other hobbies that you want to include in your camping trip, this can really effect your total weight. My friend Johan, for example, is very into photography, and always takes his big camera and lenses with him. This costs him about 1.5kg he told me. Obviously Johan is then limited to going LW most of the time, though I have seen him go UL at times.
One thing that I really like about going lightweight that should be mentioned is that it promotes creativity. You look at your gear in a whole new way and think of more than one use for each piece of gear to get the most out of less. My underwear becomes my swimwear too, my pot a sink to wash up in, socks can become gloves or pot holders while cooking, and on and on. You become better at improvising and problem solving as an added benefit of becoming a lightweight backpacker.
Last, safety and comfort should also be taken into consideration. Of course safety comes first, but keep in mind that comfort can promote safety. Being warmer while you sleep at night is comfortable, sure, but more importantly keeps you from dying of hypothermia. Getting a good night's sleep is cozy, but also allows you to be well rested to hike the next day, and more alert in the event of an emergency. So if you need to have a pillow to sleep well, take it--and remember there are lightweight options for pillows. I made my own very comfy little pillow that only weighs 47g.
If you are going into a very remote area with civilization far away, and doing more adventure style backpacking, the lightweight police are not going to arrest you for taking a few extra pieces of gear "just in case". Yet there are some people out there with enough experience and training that are able to go UL or even SUL way out in the middle of nowhere, but odds are you are not one of these people, so don't sacrifice a piece of gear that might be the difference between life or death depending on where you are going, for how long, and how much survival training you have under your belt. Some people can get away with walking into the woods with just a knife and the clothing on their back for a month, but most people can't. Know your own limitations and plan accordingly.
I hope this gives some kind of guide towards these three lightweight paths. I am not going to be able to cover all the aspects of why and how to choose each path, but this ought to give a rough idea on what goes into my decision making process when I go backpacking. It has a lot to do with what the conditions are outside, how far I am hiking, how long I will be going, what I want to do while I am out there, and that I am safe and comfortable.
What is perhaps most important is the connected issues of safety and comfort, which will vary from person to person depending on a variety of factors. What is safe and comfortable for me may not be for another person, and there are people with even more advanced skill sets of backpacking and/or survival that I may not be safe or comfortable if I packed like they do.
In short, most of the time this is how my choices look like:
LW - Winter/late fall/early spring, if traveling through more isolated/challenging areas, my own personal safety and comfort are an issue, doing a lot of fishing (large fishing kit)
UL - My go-to style of backpacking most of the time, doing some fishing (basic fishing kit)
SUL - Summer, traveling through familiar terrain, no fishing
An example of one of my UL gear lists can be found here on my blog, and my first official SUL gear list and trip I documented in great detail if you have not read these posts yet and are interested to know more about how I roll. Just check out the archives, and I hope this big, long-winded post was useful for you!