Choosing a backpack isn't a decision to take lightly. An overly small backpack won’t be able to handle all the gear you need; an ill-fitting backpack can cause extreme discomfort after just a few minutes. It is important to select a backpack that’s comfortable and that has the capacity and features you need.
Capacity
Backpacks are categorized by what length of trip the pack is good for: a day, a weekend, or a week or more. This is determined by the pack’s capacity, measured in cubic inches. A day pack can be anywhere from 750 cu. in. for a day of hiking to 3,000 cu. in. for a backwoods overnight. A weekend pack generally measures 1,500 cu. in. to 4,000 cu. in. for extended weekends, and a weeklong pack handles 3,000 to 6,000 cu. in. or more (high-capacity packs are often called full or expedition packs). Consider all the gear you’ll need for your trip before you buy a pack, so that you don’t end up choosing one that’s too small.
The Frame: External vs. Internal
Most backpacks, except for rucksacks and most day packs, have some type of frame, either external or internal. The main purpose of the frame is to allow weight to be distributed, making the pack easier and more comfortable to carry.
The first pack frames were external. External frame packs are better for heavier loads than are internal frame packs. They keep the pack away from the back, minimizing chaffing and allowing ventilation. More weight is transferred to the hips. They are better for organization because they have more compartments, and you can lash gear to the frame. However, this exposes the gear to weather and sharp objects. Additionally, the frame can impede arm movement and snag on branches. External frame packs aren’t suited to uneven terrain, which can make the pack swing.
Internal frame packs were developed later. These packs mold to the back and keep the weight closer to the body, allowing for better balance, especially on uneven terrain. They won’t snag on branches and allow uninhibited arm movement. They also offer more adjustments. However, there is basically one large compartment, so items requiring quick access must be packed toward the top. Because more weight is on the back, internal frame packs tend to make the wearer bend forward. They are also more expensive than external frame packs.
Fitting the Backpack
Many people know that a poor-fitting pair of shoes can ruin a hiking trip. But the wrong backpack can make a hike miserable even faster than can the wrong shoes
It is very important to make sure a pack is well-fitting and comfortable before leaving the store. Don’t wait until you’re on the trail to discover that the pack beats against you with every step, or puts the weight on your shoulders instead of your hips.
The first step in fitting a pack is to have someone measure your torso. A friend can do this. With your head tilted back, find the bony protrusion at the base of the neck and place a piece of masking tape there. Next, place your hands on top of your hipbones with your thumbs pointing to each other behind your back, and have the person place a piece of tape between the thumbs on the spine. Then have the person measure between the pieces of tape to get your torso length.
After you’ve determined what capacity and type of frame you want. Both the frame and the suspension (shoulder straps and hip belt) should fit your torso. Many packs come in different sizes and feature suspension that is vertically adjustable to fit your torso. Put about 25 pounds of weight into the pack, then walk around to see how it feels. Nothing should be uncomfortable. The hip belt should fit firmly around your hips, carrying most of the weight. The shoulder straps should not cut into your armpits. The pack should not bounce against your back when you walk. You should be able to fine-tune the multitude of adjustments and find a pack that feels like it’s barely there.