How to properly compare packing volume between backpacks

When comparing pack volume between backpacks, it's not enough to look at the number of liters in the product name. A 40-liter backpack can actually feel more spacious than a 45-liter one, depending on the shape, opening, pockets, and how easy it is to pack. For those who hike, camp, or need a bag for multiple days, this is a detail that affects both comfort and how well your equipment actually fits.

The most common mistake is to assume that volume is always directly comparable between different models. It is rarely that simple. Two backpacks can be labeled with the same number of liters but function completely differently out on the trail. Therefore, you need to compare both specifications and construction, not just the number on the label.

How to compare packing volume between backpacks

Pack volume is almost always stated in liters, but manufacturers don't always calculate in exactly the same way. Sometimes the figure refers to just the main compartment, sometimes it includes the top lid, side pockets, and front pocket. This means that a 50-liter backpack from one brand doesn't always correspond to a 50-liter model from another.

To get a fair idea, you first need to understand what volume actually includes. If a model has large stretch pockets on the sides and a generous front pocket, it may be perceived as more useful than a bag with the same total volume but less external storage. This is especially true for those who want quick access to a rain jacket, water bottle or wet clothes.

It's also worth considering the shape of the backpack. A narrow, tall pack may be better suited for hiking in terrain where you want freedom of movement, but it can be harder to pack with bulky gear. A wider model may be easier to organize, but can sometimes feel bulkier when you're actively moving.

Liters say a lot, but not everything

A backpack with a straight, simple tube shape often makes better use of the main volume than a model with many internal dividers, heavily padded areas, or an irregular shape. This doesn't mean one is better than the other, but it does affect how much useful stuff you actually get to pack.

If you pack light and use compressible gear, like a compact tent and a smaller sleeping bag, you can get by with fewer liters than you initially think. However, if you're carrying bulky winter gear, food for several days, or sharing a pack with someone else, you'll need more room.

What affects the perceived pack volume

Perceived volume is often more about access and disposition than the official liter figure. A backpack with a large front opening or U-zip often feels roomier than a top-loading model, as you can access all of the contents without having to empty half the bag.

Top lids can also play a bigger role than many people think. A height-adjustable top lid gives you extra flexibility when you need to pack a little more than normal. Compression straps also help stabilize a larger pack when it's not fully packed. This can be handy if you want to use the same backpack for both day trips and overnight stays.

The placement of the side pockets also plays a role. Deep pockets provide more external storage, but if they sit tight against the body or under compression straps, they become less useful. This is a typical detail that is not visible in the liter specification but is immediately noticeable in use.

Internal and external storage

When comparing models, it's wise to differentiate between total volume and functional volume. Total volume may look good on paper, but if a lot of it is in small outer pockets, you won't have the same space for larger items. For hiking with a sleeping bag, sleeping pad, extra clothes and a kitchen, the size of the main compartment is often more important than many small compartments.

At the same time, external pockets should not be underestimated. On a multi-day trip, they make your pack more accessible and help you stay organized. This is especially valuable in changeable weather when you want to quickly reach reinforcements or rain cover.

Choose volume according to luck, not habit

Many people choose a backpack based on the feeling that it is good to have extra space. In practice, this often leads to the bag being larger than necessary, and then it is almost always filled with things that are not needed. A backpack that is too big is not only heavier in itself, it also makes it easier to overpack.

For day trips, much less volume is often sufficient than for a weekend trip with an overnight stay. In the summer, a light overnight pack can fit into a backpack that feels unexpectedly compact, especially if the tent and sleeping system are chosen with low weight and small pack size in mind. During colder parts of the year, the need increases rapidly as clothing, sleeping bags and sleeping mats take up more space.

A reasonable way to think about it is to start with the length of the trip, the season, and how compact your other gear is. If you already know you're using lightweight gear, you can often reduce the volume of your backpack. If you're new to the outdoors and haven't yet optimized your packing, it's wise to leave a little extra space, but not too much.

Comparing packing volume between backpacks for different uses

For day hikes, light weight, easy access and stable carrying comfort are often more important than maximum volume. A smaller pack works best as long as it can hold water, reinforcements, a seat pad, food and a simple rain cover.

For weekend trips and shorter multi-day hikes, the backpack needs to handle sleeping gear, changing, kitchen and food without being difficult to pack. Here the difference between 40, 50 and 60 liters becomes clear, but not only in how much can be accommodated. It is also about how well the weight is distributed and how easily you can organize your pack.

For longer trips or trips with colder weather, margin is important. Food for several days takes up space, and winter-appropriate equipment does even more. In that case, it is better to choose a bag that can handle the load with a good carrying system than to squeeze everything into a model that is too small.

When bigger isn't better

A large pack may feel secure in the store but less so on the trail if the pack becomes loose and unstable. Equipment that doesn't fill the pack will move around more, especially if the compression isn't enough. This affects your balance and can make the hike more tiring than necessary.

There is a clear trade-off here. A slightly larger backpack provides flexibility, but only if it can be compressed properly and fits your body even when it is not fully packed.

Always look at the pack size of your equipment

To compare volume in a meaningful way, you need to start with what you actually carry. Two people both doing a two-day trip may need completely different backpacks depending on whether they use lightweight gear or more traditional products with larger pack sizes.

This is especially true for tents, sleeping bags and sleeping mats. A compact 1-person tent and a well-compressed sleeping bag free up a lot of space compared to older or cheaper equipment with larger volume. For those building a more efficient packing system, it may therefore be reasonable to choose a smaller bag with a better carrying feel instead of going up in liters right away.

This is also where a specialized range makes a difference. At a store like Hikingstore, it is often easier to compare products based on weight, season and packability, which helps you choose a backpack in relation to the rest of your equipment rather than as a standalone product.

How to make a fair comparison before buying

Start by checking if the volume includes outside pockets and top lids. Then look at the opening, shape and compression capabilities. After that, you need to compare it to your own packing: how big is the sleeping bag, how compact is the tent and how many days of food you need.

If you're between two models with similar liter capacities, it's often smarter to choose the one that's easier to organize and carry than the one that, on paper, holds a few more liters. Small differences in construction are more noticeable than small differences in numbers.

Don't forget about back length and fit either. A backpack that fits properly feels better, carries weight more stably, and is easier to live with on longer trips. The best volume is not the largest you can carry, but the smallest that can hold your equipment without making the pack impractical.

If you think about it, the choice becomes easier. Don't just compare liters between models - compare how much useful packing they actually can hold for your particular type of trip. That's where you'll find the backpack that works outside, not just in the product list.