The Ultimate Guide To Backpack Sizes 

 July 7, 2023

By  Keith Terrell

Backpacks are one of the best inventions on earth. These extremely useful bags come in many different designs, shapes, and sizes to accommodate professional and personal needs. From going out into the wilderness to the boardroom, there is a specific backpack size and style for you.

Backpacker Overlooking Mountains

Backpack sizes are measured in two ways: the first is by measuring the volume of the bag, which tells you how much it can hold. The volume of a backpack is measured using cubic inches or liters. The second way to measure a backpack size is through the specific dimensions of the bag (length, width, height, or depth).


It is the manufacturer’s prerogative whether the backpack measurement is in liters or cubic inches. But some backpack brands already provide both versions so that it’s much easier for the customer to understand; for example, by staying that a bag can hold 20 liters: it’s also 1,220 cubic inches in size.

different sized backpacks

The volume of a bag can be calculated by using a formula to compute its dimensions. But most backpack designers and manufacturers readily provide this information, which is determined by analyzing exactly how much all the compartments within a backpack actually store. So if your backpack has several compartments, designers measure the storage space of the small pockets in and out of the backpack, combined with the main compartment.

But not all manufacturers measure bag volume this way. Some companies also include the open pockets on a backpack’s exterior, such as its mesh pockets for water bottles, and take that into account. So even if the volume of the backpack seems like the backpack is large, it may not always be 100% accurate.


The backpack’s size refers to its dimensions; specifically, its length, width, and depth. The size of your backpack is important since it tells you how the bag sits on the body. For example, if you know how long the backpack is, you’ll have a more accurate idea of where it ends on your lower back.

Why is Size Important?

Before you purchase a backpack, understanding its size is important because it’s an indication of its capabilities as well as its limitations.

But there isn’t a single backpack size that is superior to another. It all depends on your body size and needs. A backpack that is either too small or too big for you means that the weight of your load will not be balanced, and it can cause severe back pain. In the worst case scenario, an incorrectly sized backpack can even make you topple over. You want to invest in comfort and safety, especially when you’re outdoors and far from medical attention.

Ideally, the right backpack for you is spacious enough to hold just a little more than what you are bringing and is comfortable to carry.

How To Choose The Right Sized Backpack For You

There are several important factors to consider before choosing a backpack. The market is filled with hundreds, maybe even thousands, of different styles that are designed to suit a specific use. Here are some tips to help you narrow down the perfect backpack:

tall and short hikers backpacking

Your Body Type

If you don’t choose a backpack carefully, it’s easy to end up with one that is too large or too small for your body type. Either way, it’s going to be uncomfortable no matter how or where you use the bag. The good news is that you can choose a backpack that fits your size by measuring your torso. 

The most effective way to do this is to use a flexible tape measure and ask a friend to help you out:

  • 1
    Lean your head forward then look for the bony bump found between your neck and the slope of your shoulders. This area is referred to as the C7 cervical vertebra, and it’s also the upper area of your torso length.
  • 2
    Slide both of your hands down, past your ribcage to where the top of your hipbones are. This is known as the iliac crest. Point your index finger forward and your thumbs inward to draw the imaginary line between thumbs as you do so. This is the bottom area of your torso length.
  • 3
    Stand up with your back straight, and ask your friend to measure the space between the imaginary line between your thumbs and the C7 cervical vertebra. This is the measurement of your torso length.

It also helps to measure your hips because most of the load of your backpack will rest on this part of your body. If you choose a correctly sized backpack, it’s rare that the hips or waist size to be off, but it’s still advisable to double-check anyway especially if you are going on a multi-day journey requiring you to bring a heavy load. Measure your hip size by taking a tape measure and wrapping it around the upper area of your hips, as it hugs the iliac crest. This line will be a little higher than the belt line.

Most backpacks come with adjustable suspensions which allow it to cater to individuals with varying torso lengths. If you purchase a bag with this feature, keep in mind that torso length should be the most important adjustment. If the other adjustments aren’t correct, all you need to do is reset the torso length.

Weight Capacity

Although we’ve been talking in length about size, it’s also necessary to consider the weight that a backpack can carry. Generally speaking, the larger the backpack, the greater the weight it was made to carry. But you also have to think about the kinds of things you intend to bring with you, because sometimes small items will weigh a lot, such as cooking equipment and camp gear.


The weather conditions you’ll be exposed to during your camping or hiking trip plays an important role because the elements can make or break your trip if you aren’t prepared. For example, if you’ll be outdoors during the hot summer months, hydration will be a priority which means that you’ll need space for water or hydration packs. On the other hand, adventures during cool weather will require you to have space for sweaters or jackets in your bag. When it snows, you’ll need snowshoes. And finally during winter, you’ll likely need a much bigger backpack for everything.  

Your personal packing style

All things said and done, at the end of the day you should also think about your own packing style and preferences. Some individuals have already identified what packing style fits them; rolling their clothes and other items to make it fit in a back or distributing items based on certain weight distribution. If this sounds like you, there may be a chance that you’ll need a smaller bag than you thought but always consider the larger things that can’t be folded. 

The Bottom Line

If you love the outdoors, you may be tempted to just get one big backpack and use it for all your hiking expeditions. However, this isn’t the best way to go about it because you should be opting for a bag that suits your specific need. Investing in a few backpacks that can accommodate different occasions will be the best decision you will make; it ensures you’ll always be comfortable and safe no matter your load and no matter the journey.

How To Adjust Your Backpack Fit At Home

If you’ve just bought a new large backpack with several adjustment straps, you can easily adjust the load at home for maximum comfort during your trip. Keep in mind that your legs are some of the strongest muscles in the human body, so the objective would be to adjust the straps in order to rest most of the load on your hips.

The four main adjustment straps are the hip belt, shoulder straps, load-lifter straps, and the sternum straps. When you get home, simulate a load by adding around 15 pounds into your backpack. It would be helpful to have a friend, or at least a mirror, to help examine the fit whenever you make an adjustment.

Backpack Strap

Before starting, loosen all adjustment straps. The process starts with the hip belt or shoulder straps, and ends with the sternum straps or load-lifters. Most importantly, when you finally use your bag during your excursion, remember that fit adjustment will always be dynamic.

This is why experienced hikers constantly fiddle with the straps throughout their journey in order to relieve certain pressure points as needed. Familiarizing yourself with the adjustment process as soon as you get home will prevent you from the stress of unnecessary fiddling and adjusting on the trail.

Step 1: Hip belt

  • 1
    Put your backpack on and move the hip belt around until the padding comfortably rests right above your hip bones. If it’s too high or too low, loosen or tighten the shoulder straps as needed in order to place the hip belt in its correct location.
  • 2
    Once your hip belt is in the right location, fasten its buckle to tighten it. Don’t tighten it too much; it should be snug instead of pinching at your skin.
  • 3
    The belt padding should be a little spread out beyond the front area of the hipbones. Also keep an inch of clearance on either the left or right side of the center buckle.

Step 2: Shoulder Straps

  • 1
    Tug down on the shoulder straps for a snug fit around your shoulders. However, shoulder straps shouldn’t be carrying a significant load. Otherwise this will cause pain and stress to your neck, shoulders, and upper back muscles.
  • 2
    The shoulder strap’s anchor points should be around 1-2 inches beneath your shoulder slope, around the area where your shoulder blades are. If this isn’t the case, then either your pack torso length needs to be adjusted or the hip belt is sitting at the wrong location on your hips.
  • 3
    Adjust the tension of your shoulder straps by playing around with straps until you find the sweet spot. Learn how to adjust the shoulder straps well to easily relieve pain or pressure points when you’re on your hike.

Step 3: Load Lifters

  • 1
    Load lifter straps angle at 45 degrees, leaning towards the pack body. They connect the top of your shoulder’s harness to the back panel through an anchor point.
  • 2
    Be sure not to tighten the load lifters too much. This will cause added tension that can result in pain and discomfort in your shoulders. The goal is to have it fit snugly and securely. If there is excess space in the shoulder harness, adjust it again.

Step 4: Sternum Strap

  • 1
    Slide your pack’s sternum straps around until you reach a comfortable height running across your chest. Ideally, the sternum strap would rest around an inch under your collarbones.
  • 2
    Tighten the straps and buckle it at a width that gives your arms enough freedom to move around.
  • 3
    One of the most common mistakes with adjusting backpack straps is making the sternum strap too tight. Avoid doing so because it will disrupt the harness fit, restrict breathing, and constrict chest muscles.

How To Adjust Your Backpack Fit On The Trail

There is no such thing as a perfect fit throughout your hike. At some point, what felt like a comfortable fit when you started out will somehow disappear. A good backpack fit goes through a dynamic process, which requires your continuous attention throughout your journey.

adjusting your backpack while hiking

Here are tips to keep in mind in ensuring your backpack fits well while you’re on the trail:

  • As soon as you get your backpack, make it a point to master exactly how everything adjusts by experimenting with each of the straps. Investing time in mastering how the straps work at home will save you stress and headaches while you’re on the trail.
  • When you’ve memorized what the perfect fit looked like at home, it will be much easier for you to return to it when you’re on the trail.
  • As you go through your hike, tweak the various straps to relieve pressure, aches, and pains. The only way to find out the ideal adjustments to make on the trail will be to do it through trial and error.
  • If you’re carrying a heavy load, you’ll most likely suffer from load fatigue. This is common, and the best way to alleviate it is to loosen the hip belt straps and tighten the shoulder straps. Eventually, you can reverse these steps again.
  • When you go on your hike, try to be conscious about your posture. A slightly forward tilt on your upper body will help make the load feel balanced.
  • Each time you stop for a break, remove your pack. It will give your muscles a much-needed break as you rest, stretch, and recover for a few minutes.

Common Backpack Sizes

When you’re researching for a backpack to suit your next adventure, whether it’s a weekend trip or a month-long backpacking expedition abroad, the first thing you’ll probably notice is the sheer variety of backpacks and their sizes. What do they all mean, exactly?

To answer this question, let’s look at the most common sizes backpacks are made these days and what they mean for you as the traveler. Looking at what they were made to carry, and how much of it, is a good way to tell if it’s right for the kind of adventure you’re going on.

0-10 Liters

Most hydration packs, trail running packs, and lumbar packs fall in this volume category. It’s minimalism at its best, and designed to truly only carry the essentials such as a hydration reservoir, a lightweight rain cover, and a few snacks. 

10-20 Liters

This backpack capacity is for adventures requiring you to travel quickly for no more than a day. These include day commuting to work or day hikes, where all you’ll need are food and drink for the day, light insulation layers, a headlamp, two liters of water, a headlamp, and a space blanket. 

20-30 Liters

Most daypacks fall under this category. These are made to include the essentials such as food for the day, light insulation layers (puffy or fleece jacket), rain shell, a headlamp, a small first aid kit, and a space blanket. 

30-40 Liters

This is the category where most weekend and overnight backpacks fall under. If you do go hiking, backpacks of this capacity would be suitable if you have a partner who can carry your sleeping system in their packs. Otherwise, you should be opting for an ultralight sleeping pad or a down sleeping bag for packs this size.

Backpacks that are 30-40 liters in size are usually designed with additional pockets and compartments found on its exterior and hip belts for storing headlamps, snacks, and knives. Keep in mind that backpacks this size are made to cater to various torso lengths, so it’s ideal to choose one that fits you like a glove to ensure comfort and safety during your trip.

These backpacks could fit everything you’d need for a 2 or 3-day adventure, including a lightweight sleeping bag, food for up to 6 meals, hammock/lightweight tarp/ultralight one-person tent, small sleeping pad, underwear, and an extra pair of socks.

40-50 Liters

Ideal for multi-day trips, a 40 - 50-liter backpack is suitable for carrying everything you’d need in a smaller pack including a small pot for cooking, food back for carrying up to 6 days’ worth of food, camp fuel and stove, change of clothes, a water filter, and a down sleeping back.

50-60 Liters

These backpacks are an upgrade of the 40 - 50-liter capacity, allowing you to carry everything in the previous category with additional breathing room for bigger sleeping pads and a tent.

However, many overnight and weekender backpacks are also made in this size range to cater to the essential three things you’ll need on an overnight hiking trip: shelter, sleeping bag, and pad which, while needed, are usually bulky if you don’t purchase the ultra-light varieties. Backpacks this size can hold more extra clothing, a pillow, larger sleeping pad, a tent good for 2-3 persons, camping shoes, and a synthetic sleeping bag.

60-70 Liters

These size backpacks are also used for multi-day backpacking trips which would fit all the conventional equipment and items you’ll need in the previous category, but these will also have additional space for non-essentials that would make your trip much more comfortable and enjoyable.

Many hikers prefer using this capacity for a backpack because it allows you to take more such as a larger first-aid kit, food for as much as 10 days, and extra cookware such as an extra pot or a frying pan.

70-80 Liters

If you take a pack this size, this means that being prepared for your adventure is a top priority. It could also mean that you are carrying supplies for other people, such as your kids or other hiking companions. The only limit to packs this size is the weight you can carry on your back.

A 70-80 liter backpack is also essential for going on high-altitude climbs. If being prepared is important to you, then you’ll want to maximize all the space available on these packs. It will allow you to pack everything on the previous categories plus a tent good for four, highly-insulated and cushioned sleeping pad, and a down or synthetic sleeping bag. 

Types of Backpacks and Their Sizes

There is an extensive array of backpacks in the market to suit specific needs. From 10 liters all the way to over a hundred liters, backpacks come in different sizes and styles for both indoor and outdoor use.

The kind of backpack you’ll need to commute to work while safely storing your laptop will be vastly different from the backpack you’ll use when you go on a camping excursion which lasts several days.  For this reason, there is no such way of knowing how many liters a regular backpack is.

laptop and backpacks

These are the most common backpack styles and their sizes:


Daypacks are backpacks that are designed for excursions that are only a day long. These are meant to carry things that you’ll only need for a few hours or up to 10 hours. Daypacks are usually between 8 to 30 liters in volume. Small daypacks, such as those that are less than 10 liters, are ideal for day hikes or even while you’re out traveling and exploring an attraction or city for the day. You’ll probably use it to carry snacks and refreshments, a towel or a change of clothes, and perhaps a lightweight jacket. Generally speaking, any backpack under 30 liters is suitable for use as a daypack. For half day hikes, 10-20 liters would be suitable but for a full day hike, you might want to consider getting a 30 or 35 liter daypack. 

Weekend backpack

Weekend backpacks are suitable for quick getaways lasting 2-3 days. A good weekend backpack is around 40 liters in volume, and is typically used to carry enough clothing for your trip as well as a few other necessities. Additionally, a weekend backpack should have enough space for you to bring all the clothes you need for up to three days without needing to have your clothes laundered, assuming you change outfits just twice a day at most.

Multi-day backpacks

Multi-day backpacks are used for longer trips that span several days; it could be used for trekking and hiking, as well as backpacking trips abroad. They usually come in 50 to 90 liters in size, and in the larger range can accommodate sleeping bags and a tent. If you’re going on a 5-night trip or more, opt for a backpack that can accommodate 70 to 90 liters but this is assuming you’d have your clothes laundered occasionally and pack versatile pieces that can be reused throughout your trip. For a 3-5-night trip, 50-65 liters will suffice; and for 2 nights, 35-50 liters.

School backpacks

School backpacks are those used by kids, high school students, and college students who usually have to carry a heavy load. These are usually 6 up to 20 liters in size. They are spacious and roomy; designed to carry several books, notebooks, and even a small laptop or tablet.  The same size of backpacks that are used for school can alternatively be used for sports as well. For example, the popular Jansport brand is well-known for their versatile line of school backpacks. Deciding on how many liters a school backpack is should depend on the weight and quantity of things you’ll be taking along.

Laptop backpacks

Students and professionals alike rely on various types of laptop backpacks. But determining the right laptop backpack for you will depend entirely on the size of your laptop. In this case, you’ll have to measure the dimensions of your laptop to check if it can fit inside its sleeves. Common laptop backpacks are designed to cater to 13 inch, 15 inch, and 17 inch laptops. It is entirely up to you to choose a laptop backpack that has less or more volume; some people need a backpack only to carry their laptop and few other things, while others require more spacious laptop backpacks to carry other items.

Tactical military backpacks

Used by soldiers who require heavy-duty bags, tactical military backpacks are distinct because of the kind of material it’s made with. These are designed to resist water, tearing, and is durable enough to survive even in the most rugged environments. Tactical military backpacks are also excellent choices for outdoor adventures and traveling because they are just so robust. They come in 25-50 liter sizes.

Drawstring backpack

If you’re looking for a lightweight backpack, a drawstring backpack is one of the best options out there. The material is typically made from fabric, and these are excellent choices for carrying an extra pair of shoes, or your gym clothes and a towel. Drawstring backpacks make great extra backpack storage to your regular backpack or can also be used as a lightweight carry all; most of them come in 14x18 inch sizes or 17x20 inches. 

Carry on backpacks

Carry on backpacks come in varying sizes to meet the general 45-linear-inch requirements of most airlines. Your carry on backpack shouldn’t exceed 22x14x9 inches (length x width x depth) if you want to breeze through security and prevent issues with your carry on. But when deciding how many liters for a carry on backpack you should get, check the limitations of the airline you’re flying with. 

Hydration backpacks

Used by cyclers, runners, and hikers, hydration backpacks are an efficient solution for recreational needs. These are made with an ergonomic design that places comfort above all, and security for your belongings. The most distinct feature of a hydration backpack is its hydration bladder compartment which is used to store water that you may need during your trip. It’s one of the best choices for outdoor trips, especially for storing things that you may need several times throughout your hike, run, or ride such as water and some snacks. The best way to choose a hydration backpack is by determining the capacity of its water reservoir; its most important feature. Water reservoirs can range from 0.5 liters (1.10 pounds) to as much as 3 liters (6.61 pounds). On the other hand, gear capacities for hydration packs range from under 5 liters to as much as 50 liters. 

Suitcase backpack

A popular choice among frequent business travelers, suitcase backpacks are compact and easily fit within the aircraft overhead bin. These are designed to be easy to travel with, sometimes have rollers or wheels, and are made with flyers who often go on many domestic or short flights. Depending on the size, suitcase backpacks can fit a laptop and some clothes, or more items. The most common styles in the market range from 25-40 liters.

Duffel bag backpack

This model combines the best of both worlds: duffel bags and backpacks. These are great choices for the gym and travelling, since they’re portable and big enough to carry your clothes, shoes, and toiletries while adding the ease provided by backpack straps. Additionally, duffel bag backpacks also have a very distinct design that stand out from other backpacks in the market. These hybrid backpacks can also double as weekend and multi-day bags, and can usually hold from 20 to over 100 liters. 

Compression backpacks

Also known as a compression sack, as its name implies these bags can be compressed so that you get as much storage efficiency as possible. It makes a great additional backpack or carry all, and helps ensure that you make use of all the space possible when you’re traveling. Compression backpacks are also ideal for travelers who want a compact and light bag without sacrificing storage space, which gives you a much more comfortable adventure. Compression backpacks range from 15 to 50 liters. 

Female-specific backpacks

While women can wear unisex or an appropriate men’s backpack, there are some models in the market that are designed to fit women more comfortably. Female-specific backpacks are usually designed with a curved waist belt, shorter torso length, and narrower shoulder width; features that are more mindful of the differences in a woman’s body, which typically won’t be in a man’s hiking backpack. These types of backpacks make it easier for women to find a suitable pack that they can travel with to long distances, which is an excellent option for women who want to explore the best choices for their body types in the market. 

External attachments

Lastly, if you intend to take a lot of bulky items with you, this doesn’t always mean that you’ll need to buy a second pack. External attachments are also available, made for water bottles, rain gear, bulky sleeping pads, and snowshoes which can be stuffed into your backpack’s exterior pockets. Alternatively, some external attachments can also be attached to the bottom, back, or side of your backpack so that you can use the same bag for longer trips.


Backpacks are a staple in our lives, whether you love the outdoors or not. They are extremely versatile and efficient at helping is securely store, carry, and travel with our most important belongings as we take them to journeys across the country and around the world.

With this guide, you can easily find exactly the kind of backpack whose size, volume, and style caters to your individual needs. Considering the hundreds of backpack styles in the market today, choosing the right one can be overwhelming and this is why it’s always recommended to read up as much as you possibly can about selecting the correct backpack based on size. But at the end of the day, it’s up to you to make the final decision since it’s only you who truly understands the conditions you’ll be hiking in.

We hope that this guide has helped you make a well-informed decision about finding the best backpack out of all the options out there.

About the author

Keith is a one bag traveler and the owner of Backpacks Global. His go to backpack is the Osprey FarPoint 40.

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