The Ultimate Guide to Choosing the Perfect Backpack Size for Your Thru-Hike

Struggling to choose the right backpack size for your thru-hike? This in-depth guide covers everything from measuring your torso to packing tips to help you pick the perfect pack.

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Josh Koop

I live with my wife and daughter in Katy, Texas and my local trail is the Lone Star Hiking Trail which is an amazing way to experience the Sam Houston National Park!

Backpackers out on a longer trek with 60+ liter backpacks full of gear
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When you are choosing a backpack for a thru-hike , the most important factors to consider are volume, pack weight, and weight the pack can carry. You need a backpack that is big enough to fit all of your gear, but not so big that it becomes cumbersome to carry so what size pack for thru-hiking should you choose?

Most thru-hikers will use a pack size between 40L and 60L, the more dialed in your kit the lighter your pack becomes. Many starting without previous experience will tend towards heavier gear if the approach trail is their first time hiking.

Knowing a size can give you a general idea but to really know what size your backpack is going to need to be you have to really work through much more information, as all the gear you have needs to fit but sizing the pack to yourself is vital in addition.

I will dive into this in much greater detail below and then once you have locked in all these other things you will be ready to make your gear choice and enjoy continuing your thru-hike planning and shakedowns!

How to Choose the Perfect Backpack for Your Thru-Hike

Let’s take a deeper look into all the thought that needs to be put in when looking to choose a backpack, it does come down to more than just “liking” a specific brand or style.

There are really only a few key things to think about when zeroing in on what size pack you will need for thru-hiking.

Always Buy Your Backpack Last

This may feel quite backward to many newer hikers who are looking to buy their first gear for a thru-hike, YouTube and blogs always talk about your big three being your backpack, shelter, and sleep system but you do need to know how much space your gear will take and its overall weight before purchasing.

It’s not necessarily all the smaller gear but there are some tents that need a specific width to lay flat in a backpack versus standing vertically, while this may seem silly, keeping gear vertically inside your pack makes weight distribution more difficult.

Having your shelter and sleep system let you know the space your bulkiest gear will require which will give you a better understanding of the liters of internal space you will need to look at, generally this is 40-60L to fit all your gear.

This will also give you a general idea of your pack weight overall which is another key piece of information when you choose a backpack as you need it to be comfortable to carry at the weight you will be carrying.

Getting the Right Backpack Fit For Your Body

Not all backpacks are the same size, this is a big-time mistake most people make on selecting their first backpack, what may be a comfortable fit for one person could be very uncomfortable for someone else.

Many believe that since they are short or they are tall that it determines the right backpack size for them but this couldn’t be further from the truth, you instead need to measure your back to get the right length to get maximum comfort and fit.

You need to know your torso size as packs are built to this height and then you need to know your hip circumference to ensure the hip belt will fit you as you need them to.

How to Measure Your Torso Length

You need to know your torso size to ensure you purchase the correct sized backpack from the get-go, this is a process that is easily done at home.

First, locate C-R – the bony protrusion at the base of your neck in line with your spine – and Iliac Crest – the top of your hip bones. With a flexible measuring tape, start at C-R and measure down along your spine to the Iliac Crest.

If you don’t have a flexible measuring tape, no worries, any type of string will work perfectly fine, simply mark the string at C-R and then lay it down your spine to the Iliac Crest, and then measure the string with a ruler or card measuring tape.

You want to take this measurement in inches or centimeters, whichever you are more comfortable with.

Finding Your Optimal Hip Belt Size

This measurement helps with sizing the hip belt on the backpack and getting a comfortable fit, you will want to use a hard measuring tape for this.

Start at the top of your hip bones where they protrude the most and then measure around in a complete circle, ensure the tape is level all the way around and not too tight or too loose.

You again will want to take this measurement in either inches or centimeters. Now that you have your torso and hip measurements, what do you do with them?

Check The Manufacturer’s Sizing Chart

The next step is finding a backpack that will fit those measurements, most manufacturers nowadays have built sizing charts on their websites which makes this process very easy.

If the manufacturer you are looking at does not have a sizing chart, don’t fret, simply contact their customer service and they will be more than happy to help you out.

When you find the model of backpack you are interested in, locate the torso and hip measurements on the sizing chart and see what size pack corresponds with your numbers.

As a general rule of thumb, your hip measurement should be within a few inches of the backpack’s hip belt and your torso measurement should fall in the range of the size pack.

Key Differences: Men’s vs. Women’s Backpacks

Most packs may come in a men’s versus women’s sizing and there are some key differences you should know about before making your purchase.

Women’s backpacks are built to fit the curves of a woman’s body which includes narrower shoulders, a shorter torso length, and hips that are generally wider than men’s.

Additionally, women’s packs often have an S-curved shoulder harness which contours better to a woman’s chest and provides more comfort.

Finally, the hip belt on a woman’s backpack is often narrower and curvier to fit a woman’s hips better.

Weighing Ultralight vs. Traditional Backpack Features

This conversation will probably never die, in the quest to carry as little weight as possible the push towards ultralight tends to call to everyone who enjoys this hobby long-term, it’s just true that 20 pounds wear better than 40 pounds.

The issue is to get towards ultralight tends to mean minimalizing more and a focus on pure function at the expense of all other things, for many a traditional pack with a brain, extra pockets, and even heavier, in general, is a better choice for their comfort.

Ultralight Backpacks

These are backpacks that tend to drop any excesses from materials to straps and focus on a core middle storage area with a couple of exterior pockets. For many this will even remove the hip belt itself, this is what helps to drive their weight down.

These are made from more high-tech fabrics like DCF, ULTRA, and similar waterproof materials, with limited stitching and a focus on the basics.

Choosing ultralight packs will inevitably cause the backpack to have less weight-bearing capability before becoming uncomfortable and a direct trade-off in the cost, which escalates fast the lighter your backpack becomes.

This being said, many ultralight backpacks can weigh under a pound, to around two pounds whereas traditional packs can easily weigh four pounds or more!

Traditional Backpacks

A traditional backpack has many more features and works harder to maximize the comfort and carry potential, many say they chose an Osprey because while heavier it provided them a far more comfortable carry due to construction.

Traditional packs will give you some valuable bonuses, typically in a frame to help distribute weight more across your hips than on your shoulders but then, in addition, you get more places to store gear, some people prefer to have a brain, or a lower gear storage zip below the pack for a sleeping quilt or bag.

For a lot of new backpackers, their gear will take up more liters of space or be heavier which can lead to starting with a traditional pack and evolving over time though this would increase costs versus taking the plunge the first time.

Customizing Your Pack: Handy Add-Ons and Features

This will be where you figure out which features are important to you, if this is your first backpack and you aren’t sure about these items it would be a good idea to see if you can visit an REI close to you to go through these things and try on a few packs also to see what you like or don’t.

Frame Style

Choosing whether you want a frame and the style of frame will give you a great starting point for what size backpack you need as the two are closely related.

A frame-style will distribute the weight of your pack better and across a larger surface area so it doesn’t feel like all the weight is on your shoulders alone.

It also will give you some rigidity to help support what’s inside, this can be great for things like water bladders and keeping them from being squished inside your pack.

There are a few different frame styles, internal frame packs are the most common which have the frame stay within the backpack itself, or an external frame that uses metal stays on the outside of the bag to support what’s inside.

External frame packs haven’t been popular in recent decades but can still be found, these are what you typically see in very large packs or ones designed for carrying lots of gear like on a hunting trip.

External Pockets

These are frequently found on ultralight and traditional backpacks in 3 places, both sides of the pack and then on the back of the pack in the form of some mesh whether made from a super-stretchy Lycra or a more open mesh as you see on HMG packs like the Windrider.

They can be great for storing things you need to grab quickly or frequently like snacks, your water bottle, maps, etc.

On the other hand, they do add some weight and complexity so if you don’t think you will use them it might be better to save some money and get a simpler


This is a cover on the top of a non-rolltop backpack that keeps the top of your pack closed off, it’s typically removable and can be a great way to keep gear organized and secure.

They also protect what’s inside from the elements like rain or snow if you are caught in bad weather, often they will have some type of daisy chain or attachment point on them as well so you can add gear to the outside of your backpack as well.

Extension Collar

This is what you use to increase the size of your backpack, it’s a sleeve that goes around the main body of the pack and can be cinched closed with a drawstring.

They are found on most traditional backpacks as they give you some extra space to store gear if needed but ultralight packs will often not have them to save on weight.


This largely comes down to the fabric of choice along with how the seams were sealed, while many may claim some semblance of waterproof I suggest always using a pack liner and/or pack cover to protect it from a real downpour.

Most Dyneema packs will be waterproof on their own as the material is impermeable to water but what’s inside may still get wet if not properly protected as stitches create hundreds of holes that could allow water in.

Straps and Buckles

There is a wide range of straps and buckles you will find on backpacks, from the simple but strong daisy chain found on many ultralight packs to more beefy options like what’s found on most traditional backpacks.

There will be side, back, top, and sometimes bottom straps and buckles. This can slowly add weight but may add the carry you need for a certain item like when on a trail that requires the use of a bear canister.

Identify Your Price Point

After all your other gear is purchased what you have left will help you to identify what price point you can afford for your backpack. Remember, for a big thru-hike this will be your home to transport all your gear for 6+ months so make your choice wisely!

You don’t need the most expensive option but getting something that is well made and will last you a long time is worth considering, especially since it’s what will be carrying all your gear.

Adjusting Your Pack

Most general hiking backpacks will have many possible adjustments to get the fit just right for you, from adjusting the shoulder straps to changing the distance between the shoulder straps and your body.

All of these will affect how comfortable your backpack is to wear so it’s important to take some time and experiment with what works best for you.

When out on a long hike, you’ll likely be carrying a lot of gear with you. This means that having a comfortable and properly fitting backpack is crucial. So when working to dial in the pack you want to do all these adjustments with a weight close to what you plan to carry.

Hip Belt

The hip belt’s purpose is to allow adjustments to be made to how much of the weight is carried on your hips.

This can greatly affect how comfortable your backpack is and how well it rides while you are carrying it.

They come in a variety of sizes, shapes, and materials so finding one that works for you will largely be a matter of personal preference.

Many companies will have a sizing chart on their website that you can use to find the right hip belt for your body.

Shoulder Straps

Your shoulder straps are what help to distribute the weight of your backpack evenly across your body.

They should be wide and padded well so that they don’t dig into your shoulders while you are carrying a heavy load.

The straps should also be adjustable so that you can change the distance between them and your body to find what is most comfortable for you.

Chest or Sternum Strap

The shoulder straps will also have a chest strap which anchors the straps to your body and helps to distribute the weight of your backpack evenly across your body.

This strap should also be adjustable so that you can find what is most comfortable for you but it should sit at around armpit level and pull snug but not tight like a hug just keeping it close.

Load Lifters

Many backpacks will have load lifters which are straps that attach the top of the backpack to your shoulder straps.

They help to lift the weight of the backpack closer to your body and can be very helpful in making a backpack more comfortable to carry.

Expert Tips for Organizing and Packing Your Pack

Overall there is a structure to how you pack your gear to maximize your comfort while carrying your backpack , some of this requires knowledge of your gear and what you need to ensure stays dry to maintain safety.

I personally always start with a Nylaflume pack liner, this is another level of waterproof gear inside my near-waterproof backpack.

They are incredibly lightweight but a budget approach could be a garbage compactor bag as they are thicker and generally better for the arduous journey without failing.

Bottom (Inside Your Pack Liner)

This will need to be the base for your heavier middle gear, this is most commonly started with your sleeping quilt or bag.

After this, I always include my sleep clothes which are a thin merino base layer, socks, a sleeping pad, and your puffy jacket since you shouldn’t require these all until camp.

After this is all included you twist and tie off the liner to seal it as best as possible to water getting inside the liner bag.


This is where the heavy gear will go, starting with your food bag which for 3-5 days could weigh around 3-7 pounds depending on what weight of the food you pack in for a given trip with food generally being 1-1.5 pounds each day.

Generally, you want the heaviest weights closest to the middle of your body to carry it better, if you carry it too low or too high you can have issues with how the weight shifts on your body.

The food bag can be held in place better by any additional mid-weight gear like an Appalachian Gear Hoodie or similar hoodie layer.


This is where I have my shelter when I bring a tent as it is the first thing I need once I reach camp, though I can express that honestly I am trying to figure out where the sleeping part of my hammock kit itself should go if it needs to be inside of the pack liner or not.

As a last gear item, I would have my rain gear so that it is quick to get to, since I have limited pockets externally I don’t store mine outside at this time.


This is where you should have all the gear items you will need frequently for the day or that are frequently wet and needs to be dried out along the trail.

Typically this will be gear like a guidebook or map, your tent stakes, tent fly, bathroom kit, water, your hiking snacks for the day, and a sit pad or 1/8th inch thin pad that has become popular.

Final Thoughts on Choosing a Backpack Size for a Thru-Hike

Choosing what size pack for a backpacking trip can be difficult, but it doesn’t have to be regardless of deciding on a thru-hike or if your goal is just an overnight trip with a day pack.

I hope this article has given you some helpful pointers on what to think about when selecting the right backpack for your needs and what kind of information is important in making that decision.

What was the most helpful part of this article? Do you have any other questions about what size pack for thru-hiking? Let me know in the comments!

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