Ultimate Guide to Ultralight Backpacks

Photo by Cam "Swami" Honan

What is an Ultralight Backpack?

Unlike traditional external or internal frame backpacks, ultralight backpacks tend to be either frameless or have lightweight support and suspension systems to help distribute the weight being hauled. Ultralight backpacks tend to be made from cutting edge, lightweight fabrics and hardware. By utilizing these materials, the packs can achieve a light weight (under 3 lbs) while retaining durability for extended use. Ultralight backpacks are designed to be part of an overall ultralight approach to backpacking; most ultralight packs are rated to carry no more than 25-35lbs. If exceeding the recommended max weight, the pack will either be uncomfortable to carry or may experience catastrophic failure out in the field.

History of Ultralight Backpacks

History of Ultralight Backpacks - Six Moon Designs
A collection of various ultralight packs of the past. Photo by Matthew Reed.

The oldest backpacks in the world would be considered ultralight packs by their design. The traditional frameless rucksack used for millennia could be considered the earliest version of an ultralight backpack. Post-World War II, as more Americans began to explore the outdoors for recreation, backpacking gear started to be marketed as robust and durable, and the era of heavy external frame backpacks came to be. In the 1980’s, Lowe Alpine pioneered the internal frame backpack market and a whole new era of backpacking gear came to be. These packs were well built and made from heavy weight outdoor fabrics and hardware. When empty, these packs tended to weigh between 7-9lbs, more than most modern ultralight hikers' base weights during the summer.

In the mid 1990’s, backpacking and, in particular, thru-hiking had another rise in popularity not seen since the mid 1970’s. As more people were hiking and carrying heavy gear, a new thought about going ultralight came to the forefront thanks to the very popular book by Ray Jardine, The PCT Hikers Handbook. In this book, the author outlined ways to save weight on gear so you could hike farther, faster, and more comfortably. At the time, there was no commercially available ultralight gear but Ray provided instructions for how to make your own gear and, to this day, sells patterns and kits for hikers desiring to make their own gear.

In the early part of the 2000’s, a few hiking enthusiasts started making ultralight gear and selling it to consumers. This was the start of the cottage brands of ultralight backpacking gear, one of which included Six Moon Designs. These companies pushed the limits on weight and strived to continually make their gear lighter and lighter. One lesson learned was that while the pack may be ultralight, some users' gear going in the pack was not. As a result, ultralight backpacks and backpackers were sometimes scorned by the traditional backpacking world as not being safe or the items too weak to handle a serious hike.

With time, the rest of the gear to go with the pack caught up to the early designs. Manufacturers also learned from their earlier designs, and have since reinforced weak areas, increased durability as needed, and have found the correct balance between weight, comfort, and durability, although it may mean offering a backpack slightly heavier than their earlier models.

Ultralight Backpack Design

Wy'east Daypack Prototype. Photo by Whitney "Allgood" LaRuffa.

Most ultralight backpacks have a similar design and, looking at at today’s market at a glance, one might say “these packs all look alike”. This is because ultralight packs take a simple approach to design, keeping things clean and straightforward, with little to no extra “bells and whistles” except for, say, that whistle on your sternum strap. By eliminating all the extras and utilizing one main compartment and a few exterior pockets, these packs can fit all the gear you need while keeping the weight down.

Ultralight packs tend to be designed as either a frameless rucksack with no suspension system or have a lightweight support system consisting of an internal stay or stays or a pack frame sheet. All these designs have their place in the ultralight world depending on the season one will be using the pack, the base weight one plans to carry, and user preferences on weight to comfort ratio.

Wy'east Daypack Prototype. Photos by Whitney "Allgood" LaRuffa.

While the ultralight backpacks from various manufacturers may have the same look consisting of a large main compartment, a water bottle pocket on each side of the pack, and a large mesh front pocket, the similarity generally ends there. Each pack company has their own take on suspension for load transfer or lack thereof. With a variety of available options, from aluminum pack stays, carbon fiber suspension, Delrin stays, and even modern polycarbonate frame sheets, each pack's unique suspension system provides a differing load transfer and comfort for the user.

Ultralight Backpack Materials

Ultralight backpacks are constructed using the latest in ultralight yet ultra-durable materials. The fabrics for the main pack body generally have high abrasion resistance, can hold up to extended UV exposure, and some are even waterproof. Six Moon Designs offers backpacks in Robic Nylon, X-Pac X4 and Liteskin fabrics. Robic nylon is an extremely popular nylon fabric that has proven itself year after year as a fabric of choice for backpack manufacturers. It is lightweight, durable, and dries fast when it gets wet. The X-Pac X4 and Liteskin fabrics by Dimension Polyant are a modern material derived from the sailboat racing world. These fabrics are a multi-layer laminate of modern filaments that are treated with a waterproof coating. You can read more about them here.

From left to right: X-Pac VX21, X-Pac LS21, Robic Nylon

The front pocket on most ultralight backpacks is constructed out of either a mesh or stretch woven material. This construction allows the pocket to expand as needed and allows for airflow during the day. A popular technique among ultralight hikers is to store their wet shelter in this pocket during the day so that it may dry out while they hike along the trail. Six Moon Designs backpacks utilize a stretch woven material. Over the years, we have found this material to be more durable and, with the lack of mesh holes, it tends to get snagged less on brush along the trail.

Hardware on ultralight backpacks is another crucial area where manufacturers can achieve weight savings, while still providing very reliable and durable options. In recent years, manufacturers of buckles, clips, and other hardware items have realized the desire for smaller profiles to not only save weight but also provide a cleaner aesthetic for the products they are being used on.  

With the advances in material manufacturing over the years, and an expanding collection of new, cutting-edge fabrics and hardware coming to the outdoor market, there has never been a better time for advances to be made in ultralight backpacks.

Ultralight Backpack Volumes & Typical Use Cases

Ultralight backpacks generally range in volume from 30L up to 65L, with the most popular volume among long distance hikers falling between 40-50L. The volume of pack one decides to carry greatly depends on the volume of their gear, the amount of food and water they plan to carry, if a bear can will be needed where they are taking the pack, and how much clothing they will need based on weather conditions. Other things to consider when choosing the volume of your backpacks is your preference of having all your items inside the main body of the pack or if you plan to lash and attach various items on the outside of your backpack instead. Just be aware that many hikers tend to fill their entire backpack regardless of the volume, so one can clearly see that a 65L backpack is going to most likely be heavier than a 30L backpack when it’s time to hit the trail.

Various Pack Sizes. Left to right: James Lamers using the Wy'east Daypack, John "Phantom" Ormsby using the Swift X, "Triple Threat" using the Minimalist V2, Matthieu Leroux using the Flex PR.

Knowing that most hikers will use a 40L-50L backpack, you may ask yourself, “Why even consider a 30L or a 65L backpack?” The answer is because each backpack has its place. Let us explore the typical use scenario for each volume:

  • 30L backpacks are a great choice if you have a super ultralight kit and primarily hike during the prime season of summer, where you need minimal clothing. A 30L backpack can haul about 5 days of food, 2-3L of water and your gear comfortably if you have a light kit. Ideal uses for a backpack of this size would be weekend trips of 1-2 nights, a thru-hike where you can resupply every few days, and a summer hike when you need minimal extra clothing.
  • 40L backpacks are a fantastic choice for most hikers and a very popular size among long distance hikers. This volume of pack will be ideal for those who have mastered an ultralight kit and/or are venturing into the backcountry in cooler temps when they need some more clothes. When needed, these packs can generally fit a bear can inside along with your gear. Ideal uses for this volume pack would be a thru-hike along a major trail, a trip into the Sierra during the summer, and shoulder season hikes for those with very refined kits.
  • 50L backpacks are the standard workhorse of the ultralight backpacking world. These backpacks can do it all from a quick weekend backpacking trip on a local trail to a thru-hike of the Continental Divide Trail. These packs can easily fit one’s gear, a bear canister, food, water, and almost anything else an ultralight hiker carries. With ample space for fitting all your items in the main body, you will have a neat and tidy pack with less of a chance of losing something while hiking. Ideal uses for this pack volume are pretty much any hike where you may need to carry extra clothing, up to 7 days of food and multiple liters of water.
  • 65L backpacks are a great choice for people new to ultralight hiking or those making a transition from more traditional backpacking gear to ultralight gear. These packs are also great choices for winter activities where one may need to bring additional layers of extra fuel, food etc… These packs can easily fit bear canisters, a week’s worth of food, and all the water one may need in the most dire of environments. Typical uses for a 65L backpack would be extended weeks in the backcountry, thru-hikes, shoulder season or winter trips, and anytime one needs some extra space for their gear.

Internal Frame Packs vs External Frame Packs

Left: Modern Internal Frame Pack. Photo by Naomi "The Punisher" Hudetz. Right: External Frame Pack. Photo courtesy of Whitney "Allgood" La Ruffa.

Most modern ultralight backpacks use an internal frame or support system as opposed to a more traditional external frame pack. The main reason that internal frame backpacks became the norm in the mid to late 1990’s is these packs tend to be more comfortable to carry, and they have a smaller profile than an external frame pack. External frame packs utilize a metal frame, and are great for carrying a heavy load of 50-90lbs, but they tend to be heavier in weight and also very large and bulky. One major advantage an external frame pack has over most internal frame packs, besides being able to carry a heavier load, is that, by design, they have more airflow along the back helping with the dreaded back sweat most hikers deal with during the day.

Internal frame packs have come a long way over the years. The initial internal frame packs used elaborate internal support systems that rivaled the weight of most external frame packs. Over the years, though, these support systems have been adapted into an ultralight fashion. Some manufacturers used what is known as a framesheet, a rigid plastic or similar material sheet that provides the main support of the pack. The Sheet is covered in foam to be comfortable on one's back and this sheet is used to distribute the weight.

The other category of internal frame packs is ultralight packs that utilize internal stays to help provide support and load distribution for the pack in a lightweight and flexible option. These packs generally utilize one continuous Delrin or aluminum hoop stay that helps transfer the load from the upper part of that pack down into one’s hips. The other option often used is a pair of Carbon Fiber stays. While these stays are ultralight, they can develop micro fractures over time causing failure and they tend to become brittle in extreme cold.

Shoulder Harness Options

Ultralight backpacks generally use a traditional set of lightweight shoulder straps with a sternum strap and pockets on the straps for holding a phone, camera, map, sunglasses, or whatever else you like. These straps are generally a J-strap design or an S-strap design. Six Moon Designs offer both of these types of straps along with a very unique 3rd option: a running style vest.

J-straps are the standard shoulder strap found on most backpacks. These straps are the one size fits all design and for most people they work just fine for being a comfortable shoulder strap to help you carry your load all day long.

S-straps were originally designed with female anatomy in mind to provide a more comfortable strap to help carry a load without causing any pain. These straps come over the shoulder and quickly wrap down and away from the chest. In recent years many barrel chested hikers have also discovered that these are a very comfortable option.

Six Moon Designs Flight Vest Harness in use. Photo by Whitney "Allgood" La Ruffa.

Running style vests prove a unique option for a backpack. These vests help spread the load from the shoulders to the core of the hiker, while also providing ample pockets to access items all day long. Six Moon Designs has been offering a vest option since we began making packs 20 years ago. Our founder, Ron Moak, developed the concept when he needed to find a way to get the weight off his shoulder and back to prevent back spasms after losing a large area of back muscle to cancer. Our vest suspension utilizes 6 points of suspension from the top of the pack to the bottom of the pack. This allows for the maximum distribution of weight and provides one of the most responsive suspension systems out there. The pack essentially becomes an extension of your body and, when quickly moving downhill, the pack will move with you as you turn a switchback instead of trying to pull you the opposite way.

Water bottle Pockets and Hydration Sleeves

“Hydrate or Die” are words to live by when you are hiking countless miles day after day. The two major ways most ultralight hikers carry their water is either in water bottles on the outside of their pack or by utilizing a hydration bladder with a long tube they can drink from while hiking. While the best hydration option comes down to the hiker’s preference, most ultralight packs provide a good solution. Standard on most ultralight backpacks are two water bottle pockets found on each side of the pack. These side pockets will generally hold one or two 1L water bottles on each side. The other option is to use a hydration bladder and place it inside your pack. Most ultralight backpacks provide a hanging hydration sleeve inside to put your hydration bladder in for a secure inner spot. The hose can then be placed through one of the hydration ports located above the shoulder straps on the pack.

Load Lifters

Load Lifters on the Swift X. Photo by Spencer Raap.

Load lifters are the straps that go from the top of your shoulder straps to the top of the backpack. These straps help shift/lift the weight off one’s shoulders, helping reduce the downward force on one’s trapezius muscles. Load lifters can also be adjusted to help balance the weight of the backpack when going uphill or downhill. On a long steep ascent, you can tighten the load lifters, this will shift the pack weight forward toward the mountain and not be an opposing force as you climb up. On a descent the load lifters can be loosened allowing the weight of the pack to shift further behind you creating a counterbalance while walking downhill. Next time you are out on a hike try playing around with your load lifters and find the perfect balance for yourself.

Hip Belt Options

Ultralight backpacks have 4 categories of hip belts: no hip belt, a simple webbing belt, a padded, lightly structured belt, and finally a structured hip belt. The hip belt serves two purposes on an ultralight backpack, securing the pack so it doesn’t move around when navigating uneven terrain, and providing a way to distribute weight off the shoulders and into the hips. Most ultralight hip belts now come standard with pockets on each side, which are great for keeping a compass, headlamp, snacks, a map, lip balm and other sundries one may want easy access to while walking.

Hip Belt Types and Use


Not utilizing a hip belt is not recommended for most people as it forces all the weight of your backpack on your shoulders (unless you use a Six Moon Designs Flight Vest system). This is generally a technique used by the Super Ultralight hikers with base weights of -8 lbs.

Simple Webbing Belt

A simple webbing hip belt is a ‘no frills’ hip belt option that is meant more as a way to stabilize a pack when rock scrambling or hiking on uneven terrain. It’s a clean, simple belt that can often be removed when not wanted.

Padded Hip Belt

Padded hip belts are the most common hip belts among ultralight backpacks. Often made with either EVA foam or 3D mesh, these hipbelts are soft and flexible, but wide enough and engineered to handle the shift of weight from the shoulders into the hips. These hip belts are ideal for loads up to 35lbs.

Structured Hip Belts

A structured hip belt is a beefy, more rigid hip belt that is designed to handle a large amount of weight being shifted into one’s hips. These belts are often made using a rigid, stiff material along with EVA foam to provide a rigid belt that is still comfortable to wear all day long. Structured hip belts, like the Six Moon Designs Standard Hip Belt, are designed for loads over 35lbs and can provide a tremendous amount of comfort when one is needing a little extra support in the field.

When to Use an Ultralight Backpack

SMD Founder Ron "Fallingwater" Moak using a homemade Ultralight Backpack on the PCT (2000).

For years, ultralight backpacks were seen as fringe in the backpacking world, with only the most extreme hikers utilizing them. This mind set has shifted, and now ultralight backpacks are ubiquitous with hiking. So, when should I use an ultralight backpack? Well, anytime you go backpacking would be our recommendation.

SMD Founder Ron "Fallingwater" Moak using a homemade Ultralight Backpack on the PCT (2000).

Ultralight backpacks have been used for traversers of the Brooks Range in Alaska, thru-hikes of the Triple Crown Trails (Appalachian Trail, Continental Divide Trail and Pacific Crest Trail), weekend hikes, FKTs (Fastest Known Times), and really any hike you can think of. There are times where an ultralight backpack is not the right tool for the job such as a winter mountaineering trip when you need to carry a large amount of gear. Ultralight packs are not designed or engineered for heavy loads. So, if you need to carry 40-50 lbs into the backcountry, we recommend you go for a more traditional pack designed to handle that kind of weight (or consider the Six Moon Designs Flex PR pack).

How to Choose the Correct Ultralight Backpack

Fusion 50 Six Moon Designs
Hiker choosing an ultralight backpack over a traditional backpack at AT Trail Days. Photo courtesy of Whitney "Allgood" La Ruffa.

Choosing the correct ultralight backpack is crucial for making sure you will have all day comfort when on the trail while also having all of your gear safe and secure. There are a few steps one should take in the selection process to help guide them to the right pack for them:

  1. Define what season(s) you will be using the pack.
  2. Determine if you want a frameless or an internal frame (sheet, multiple stays, or hoop stay) pack.
  3. Decide if you want to be able to fit a bear canister inside the pack.
  4. Have a rough idea of the volume you think you would like to carry.
  5. Determine what features you want the pack to have (exterior pockets and configuration, storage areas, materials, etc).

Once you have figured out most of these variables, and narrowed down your choices, the next step would be to get the pack loaded and fitted to make sure it’s going to work for you. The best way to do this, and what we recommend to people coming to the shop for a fitting, is to gather all your other gear, clothing, a few liters of water, and, if possible, a typical amount of food you may carry on a trip. Then, take all this gear and load it into the packs and walk around with it for a bit (make sure to know the return policy before taking a backpack outside for this, most companies allow free returns/exchanges if the gear is clean and in new condition). With all the gear loaded, now is the time to adjust the pack to your body. If the pack has an adjustable torso system try adjusting up or down to find the right fit.

Other areas to adjust would be the shoulder straps, load lifters and their position on your shoulder strap, and the hip belt (generally ensuring you have the right size hipbelt with some adjustment up and down for when you have a change in weight on a long hike).


Group of hikers using the ultralight Swift X backpack on Mount Hood.

Ultralight backpacks have come a long way in both quality and comfort since first being introduced to the marketplace a few decades ago. With numerous options, configurations, material choices, and an overwhelming number of personal opinions about what is the “best ultralight backpack,” it can seem overwhelming to decide which pack is right for you. By taking the time to consider what options are most important to you, your estimated base weight, the total weight of the loads the pack will need to carry, and what size of backpack you would like to carry will all help you ultimately decide which is the best pack for you.

No matter what pack you decide to go with, remember that gear is merely a tool for getting you outside to enjoy the natural world around you, calm your mind, and embrace the wonders of nature.

Swift X
Six Moon Designs Silver Shadow Hiking Umbrella Open


36 oz - 1021 g


X-Pac VX07, LS07, VX21, LS21

Best For

Long-distance hiking

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Minimalist V2


35 oz - 1002 g


X-Pac VX21, LS21, Robic Nylon

Best For

Long-distance hiking
Bear Country
Triple Crown Trails

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Flight 30 Ultra
Six Moon Designs Silver Shadow Hiking Umbrella Open


26 oz - 743 g


X-Pac VX21
Robic Nylon

Best For

Trail Running
Super Ultralight Backpacking

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Wy'east Daypack
Six Moon Designs Silver Shadow Hiking Umbrella Open


20 oz - 580 g


Robic Nylon

Best For

Day Hiking
Peak Bagging
Every Day Carry (EDC)

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