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How to choose a backpack: size guide and fit for 2021


Choosing the perfect outdoor backpack for your activities can make or break a trip. A good backpack should be suitable for the length of your absence and properly adjusted to avoid pain or injury. Here’s how a backpack size guide can help. But the best backpacks should also have the design features you prefer to make sure you can pack efficiently and have access to everything you need. While many people make the mistake of choosing a backpack based on how they look, this is far from the only thing that should be on your mind. Fortunately, you can have it all if you know exactly what to look for when shopping online or in-store.

How to measure the torso for a backpack

Group of people hiking with short term backpacks.

While shopping in a store is helpful in getting a good backpack fit, it is also possible that the packs in stock and available in store may not meet all of the criteria for your perfect pack. That is why it can be very helpful to know how to measure yourself correctly or with the help of someone else. This allows you to shop online and order the correct size backpack.

To get the correct measurements to find the best size, start with your torso measurement. You can start by finding the bony spot somewhat protruding at the top of your shoulders and the base of your neck when your head is tilted forward. Then find the middle of your back between the top of your hips. The measurement between these two points will be the length and size of your torso. To measure your hips for a backpack, measure around the top of your hips so that the tape measure crosses the same spot between the top of your hips on your back.

With these two measurements, you can use the guidelines on the websites of the backpack brands. Once you have a backpack that generally fits, you can adjust the shoulder straps, hip belt, and more to tune the pack for the perfect fit.

Read more: Best backpacks for men

Selecting a volume

Two people with medium sized backpacks standing at the railing in the forest.

Then, in a backpack size guide, there is the volume of the backpacks. Once you know the right size of backpack to look for, you need to figure out how much volume you need in a bag. Growing up is not always better. The larger the backpack, the higher its basic weight, in general. Also, the larger the bag, the more you can store, which can lead to overpacking or excessive weight when not needed. To select the best volume for a backpack, it is important to consider what type of hike you do most often or what the bag will be specifically used for.

The day hike, for example, requires a backpack that is usually no more than 25 liters. Backpacking weekends or 2-3 day treks can be well served with a bag of up to 50 liters. Those on a week-long trip of up to five days should look at packs between 60 and 85 liters. Finally, hikes or backpacking trips that will last longer than a week probably require bags containing a minimum of 75 liters and more. Keep in mind that those looking for a backpack that can do double duty – day hikes and longer hikes – should consider a backpack with a built-in removable backpack.

Read more: Best hiking backpacks

Models and accessories

Close-up of the backpack's snap button closure and mesh padding along the back.

With the most important basic components of backpack shopping, hikers and backpackers can then consider the styles and accessories offered by the different packs. Two of the most basic styling options to consider are the frame styles and level of padding of the different packs. The amount of padding simply depends on the sensitivity of your hips and back when carrying the weight of the bag. So backpacks probably don’t require a lot of padding, but some people may prefer more cushion when carrying heavy loads for a weeklong hike.

The packs may have no frame, an internal frame or an external frame made of a set of metallic materials. The main hikers who opt for a frameless bag tend to be ultralight backpackers who are very concerned about how much luggage they have to carry. External frames are known for their ability to withstand heavy loads. Internal frames, however, are the most popular backpack option. Internal frames are the most technologically advanced and often incorporate suspension systems that relieve the weight and pressure of the pack on the hips and back. Internal frames are also designed to help hikers keep a secure and balanced footing when walking through varying terrain.

Outdoor hiking backpack perched on a rock with water bottle pocket.

The next thing to evaluate when shopping is the accessibility afforded by the bag for packaging and access to items during the ride. Those who like to use a hydration system should look for a water reservoir while those who prefer water bottles may like exterior pockets for easy access. Elastic storage cords or mesh and other fasteners are also helpful. These options allow you to stuff a raincoat, wet socks, sleeping pad, water shoes, etc.

The internal organization of the pack is also important to consider. Some have special compartments to separate items that need to be kept dry, such as a sleeping compartment for the back. There may be smaller pockets to keep your valuables like keys or cell phone safe and in place. The hip belt will likely have a smaller pocket for storing snacks, a compass, and a map. Those who like to keep things simple may want to have a bag without compartments or pockets and use plastic bags, storage bags or waterproof bags to keep things safe and organized inside the bag.

Read more: Hiking checklist

Hiking man with bright red backpack on a green field.

Finally, don’t forget to think about the backpack’s ability to repel water. Most backpacks are not waterproof, but they tend to have a water resistant coating to prevent water from soaking and soaking the entire bag. But water can still get into the seams and zippers. This is why it is essential to keep a rain cover, dry bags or garbage bags handy. Bag covers can fly off in open conditions and in high winds. But storing items in a variety of plastic bag or dry bag sizes can work in a pinch to keep anything that needs to stay dry inside the bag that way.

No matter how long you plan to stay outdoors or what style of hike or trek you plan on doing, take the time to think about your habits and how you want to stay organized on the trail. Understanding how you are doing and want to use your pack will make it easier to select the best option.

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