Hunter with backpack on

Backpack Buying Guide

Next to a good pair of hiking shoes, a good backpack is essential for spending any time in the field.

And, like that proper-fitting boot, you should wear your backpack just as comfortably – proper size, proper fit and comfort and proper utility. Determining each factor is critical in selecting the right backpack. Fail to take any one into account and you’ll regret it within a few steps down the trail.

Alps Mountaineering Red Rock External Frame Backpack.
Alps Mountaineering Red Rock External Frame Backpack.

Beyond day packs used by students and those with specialized compartments for photo equipment and similar uses designed into pockets and dividers, there are two types of backpacks used by intrepid wanders and pack-in outdoor enthusiasts, external and internal frame packs.

External Frame Packs
The traditional “backpack” has an external frame, first of wood, then of metal tubing (usually aluminum). The bag or pack is attached to the frame and all the straps as well as any other attachment points are secured to the frame or pack. Typically, the sleeping bag was stowed outside the pack, on a shelf built into the bottom of the frame. Some external frame packs are capable of carrying incredible loads, sometimes over 100 pounds! Because they can restrict movement and flexibility, external frame packs are often used for trail hiking or expedition camping where climbing, skiing and other such activities will not be the major activities.

MountainSmith Apex 60 Backpack

Internal Frame Packs
Internal frame packs have a support structure integrated into the layers of the back to give it form and strength. There is no framing support visible from the outside. Strength and form come from stays (bars, rods, tubes), polyethylene panels, used alone or in combination , incorporated into the back or along the sides of the pack. Internal frame packs can also carry large amounts of weight, but tend to allow the carrier more agility and ease of movement. Backcountry skiers, climbers and others who require body movement and positioning often prefer the flexibility of the internal frame pack.

Glossary of Backpack Terms
Backpacks have their own terminology to describe components, features and other aspects to consider when deciding upon which kind of pack to buy. Before discussing the following components in more detail, here’s a short review of several backpack terms:

Torso Length – measured from the base of the neck, down along the contour of your spine, to your upper hip ridge. Torso length is a critical measurement that will determine what size pack you should wear to assure the most comfort, regardless of the ultimate carrying/packing capacity of the pack you ultimately select.

Hip Size – Similar to your waist measurement, knowing the circumference around your hip ridge will help you select the proper-sized hip belt used to support the majority of the weight of your backpack.

Pack Size/Capacity – Packs come in a variety of sizes, expressed in liters (and often further expressed in cubic inches). Common size designators (S, M, L, XL) are typically expressions of ranges of volumes within a style or model of backpacks.

Packbag – The bag or pack itself, typically made from Cordura or nylon packcloth. Some bags, such as rucksacks and “Duluth” canoe/portage packs are still made of canvas. Ultralight packs are often made of specially-coated, lightweight nylons.

Suspension System – Coupled with torso length, this is an equally important component of a backpack unit as far as proper fitting and comfort are concerned.  Suspension systems are either fixed, adjustable or interchangeable. The suspension system incorporates all the following components that provide the load-bearing support of the backpack:

  • Hip Belt – At least 80 percent of your load should rest on your hips. The correct size of hip belt should be adjustable and padded to provide proper fit and support.
  • Shoulder Straps – Designed to help position and secure the backpack to your body. They are not designed to carry the bulk of the weight of the backpack.
  • Load Lifters – Used to adjust and shift some of the weight of the pack off your shoulders, to change the angle of the pack in relation to your body/back. They should come off your pack at about a 45-degree angle.
  • Sternum Strap – Adjusted across your chest and used to pull in on your shoulder straps to keep them from slipping off.
  • Stabilizer Straps – Located on the sides of the hip belt and used to make adjustments to that belt to best secure the load for comfort and balance.

Framesheet – A stiff, plastic board along the backside of the internal backpack used to provide rigidity against twisting or shifting. It can also provide protection from hard edges within the backpack.

Attachments Points – External clips, loops, sleeves, and other options for securing loads to the outside of the backpack. Specialty packs typically offer options to attach specific gear and accessories.

Top Lid/Pockets – Additional pockets and covered sleeves for extra storage on the outside of the pack. Some backpacks might offer compartments or dividers within the bag as well.

Ventilation System – Typically either a mesh network across the back of the pack to provide a circulating air space between the torso and the pack. Others have a series of channels to draw cooler, drier air between the wearer and the backpack.

Hydration Compatibility – A pocket for a water bladder is designed into the pack for inclusion of a personal water reservoir. Some packs have elastic mesh pockets for securing a water bottle to the outside of the pack.

Rain Cover – A form-fitted covering to shelter and protect zippers and seams from rain. You can also use a heavy-duty trash/lawn bag.  Sleeping bags are stowed outside of an external pack so should be thoroughly protected in a waterproof bag.


While your physique will generally affect how big of a backpack you should carry, the main factor will be what you want to bring along based upon the type of activities you’ll be engaged in pursuing. Occasional weekend outings at backcountry or walk-in campgrounds may necessitate an average-size pack to carry in the essentials as well as a few favorite toys or treats.  Extended trips or those involving other activities such as fishing or photography may require extra volume for specialize gear or extended-stay supplies.

Anticipating your needs and your ability to carry loads based on your physique and other considerations should all help determine what size backpack you should use.

Watson's Backpack Buying Guide 5-14 SPRTSMNSGDE-TORSO MEASURETorso Measurement – Your height is not the determining factor in selecting the proper pack size. Rather, it’s the distance from your C7 vertebrae (that slightly protruding hump at the base of your neck when you tip your head forward. From that hump, down along the curve of your spine to the center point where an imaginary line connects the top of your hips (that protruding ridge on each side just below your waist) is your torso length. This is the measurement used in determining your proper backpack size.

Backpack frames are sized from Extra Small to XL/Tall, based upon torso lengths, usually in about 2-inch segments.

Hip Measurement – Another sizing factor is the measurement around the top of your hips. Called the lateral line or Iliac Crest, it is determined just as you would your waist, only lower. Because 80 percent of the weight of the pack will be supported at this point, it is critical, along with the torso measurement, to be as accurate as possible. Again, common sizing designations are based upon a range of these measurements.

Backpack Volumes – You may notice backpacks have outdoorsy names followed by a number. That number typically represents the volume, in hundreds, of the capacity of the bag in liters for the middle/medium size in that particular model. A “Boundary 60”, for example would be the middle range of a bag series designed with space for holding 60 liters in volume. One liter is equal to about 63 cubic inches so a “60” bag would hold almost 3800 cubic inches (or a little over 2 cubic feet) of gear. Forget the math and just know that bigger numbers mean more space. Excess space may encourage you to carry more gear than you really need; less may mean you leave behind critical equipment you should have along.

Watson's Backpack Buying Guide 5-14 SPRTSMNSGDE-LITER CONVERSIONWhile size, use and personal preference are all factored in when determining which backpack to choose, the general volume/capacity sizing range of backpacks among most manufacturers fall into four basic use categories:

  • Day use:  less than 2500 Cubic Inches/ 15-40 Liters
  • Weekend: 2500-4000 Cubic Inches/ 30-65 Liters
  • Multi-week: 4000-6000 Cubic Inches/ 55-95 Liters
  • Expeditions: greater than 6000 Cubic Inches/ 95+ Liters.

Comfort plays a big role in a properly fitted backpack. Using torso length and other fitting measurements as your basic guides, there are a few other factors that enter into assuring that you will be able to carry a loaded backpack comfortably and safely throughout a multi-day adventure.

It can’t be stressed enough that the weight of your bag is supported by your hips. Therefore it’s critical that you have the proper suspension system for the loads you expect to bear securely and comfortably.

There are three types of suspension systems:

  • Fixed – While they vary by torso lengths, beyond fastening, a fixed backpack offers no adjusting for repositioning or shifting of straps and belts. The advantage is a firm, solid pack. It is critical that you select the proper bag based upon an accurate torso measurement.
  • Adjustable – Shoulder strap harnesses can be moved up/down to fine tune the carrying of the pack. This can also enable you to adjust the load, particularly if sore spots occur.  Adjustment mechanisms (Rip and Stick Closures, for example) will vary among manufacturers.
  • Interchangeable – Different shoulder straps and hip belts can be selected to help fit the backpack to a particular body style, especially if the wearer falls outside the standard range of averages.

Watson's Backpack Buying Guide 5- 14 SPRTSMNSGDE-BACKPACK COMP.UTILITY & TIPS

  • Women’s backpacks – These tend to have shorter average torso lengths, conical-shaped hip belts and narrower shoulder harnesses. Anyone with a narrower frame may find these a better fit.
  •  Advancements in gear means lighter weight, but perhaps some loss of convenience.
  • Internal frames mean a closer fit, a more flexible yet stable load and more overall movement by the wearer. They are preferred by those whose activities include movement and constant body shifting (skiers, climbers, backcountry scrambling, etc.).
  • External frames allow for heavier loads and offer more compartments. They also enable carrier to walk more upright but are better when used on defined trails as opposed to backcountry bushwhacking.
  • Pack internal frames with heavier gear low and centered; pack heavier gear higher and centered in external frame packs. In both cases, keep the load as close to your spine as possible.
  • Hip Belts should be large enough and padded to properly support the load. A properly fitted belt should have a gap of about 4”-6” between the strap end of the padding and the buckle in front once tightened. You can even get molded hip belts – heated and formed to your exact hip region. (Most belts will conform to your shape over time anyway).
  • Shoulder straps do not need a lot of padding since they shouldn’t carry the brunt of the weight. They should feel comfortable. The padding on a properly fitted shoulder strap should end about 2”-3” below your arm pit.
  • The larger the backpack, the longer and narrower it should be for greater freedom of motion/stability.
  • Compression straps help snug up the contents and adjust balance and stability.
  • Spindrift collars added to the top of the bag help you stow more gear into your pack.
  • When selecting a day pack, consider a padded internal pocket for a lap top. Specialized daypacks such as those designed for cameras and lenses also work if you need to carry other small pieces of equipment afield. Consider a variety of external attachment points on a day pack.
  • Use your knee to support a loaded pack, insert one arm through the strap, hoist and swing the pack over and across your back while you slip the other arm through.
  • Carrying too much weight, and/or carrying it wrong can lead to injuries now and for the future.

There are many good quality manufacturers of backpacks offering a variety of choices among their models. Making sure you have the proper fit and volume for the type of packing you expect to do is the first of many steps in finding the backpack that is right for you.

(The above guide includes a compilation of information available from among a wide range of backpack manufacturers).


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