To accommodate a variety of body types, activities, and environmental conditions, manufacturers make backpacks in a range of designs and sizes. This allows you the user to choose the correct size and the most comfortable pack available.
Day Packs (15 - 35L)These small packs that have little or no internal frame to support loads, the cargo weight is supported by the shoulder straps. Daypacks are great for short, minimal equipment outings like day hikes. Helpful features are a waist belt to keep your load centred and padding along the back for added comfort.
Alpine Packs (35 - 55L)These medium-sized packs usually have some internal stiffeners and a more substantial hip belt that bears some the load. Their load capacity makes them useful for equipment intensive activities like ski touring and climbing, or even light overnight jaunts.
Backpacking Packs (55 - 75L)This size is designed for multi day hiking trips. They have a frame that gives structural rigidity and transfers the load from your back and shoulders to your hips.
Women's BackpackAll good quality rucksack manufacturers also make harness systems especially designed to fit the female form. These harnesses feature:
• Reshaped hip belts (proportionally larger and more cupped).
• Redesigned shoulder straps (positioned closer together at the neck and shaped away from the chest).
• Pack shape that is keeping with the proportions of the harness.
ConstructionPacks receive a lot of abuse. To ensure your choice is up to the test, look for these features:
• Durable fabrics like pack cloth or Cordura(especially in high-wear areas).
• Tightly stitched seams. To test for this, pull on the seam where the straps are sewn into the pack it should be difficult for you to see any stitches.
• Inside seams should be bound (covered by fabric) so they are less prone to wear.
• Bar-tacked stitching at stress points and load bearing surfaces.
• Weather-resistant urethane coatings that provide some protection from the elements (although any backpack will leak to some extent through its stitching).
• Beefy, strong looking zippers.
Know your torso lengthLack of this knowledge often causes an uncomfortable realization, after the fact, that the pack doesn't fit correctly. The reason you must measure your torso, rather than guess what size pack you should have, based on your ability or size, can be illustrated as follows: a large, tall person can have a short torso (and long legs) thus requiring a smaller pack. A shorter, smaller person can have a longer torso (and shorter legs) and require a larger pack. All pack makers design their packs with your torso in mind. Thus, measure your torso, preferably before purchasing.
To determine your torso size, ask a friend or family member to help you, if possible. You will need a tape measure or tailor's tape to measure along your back from the seventh vertebrae - the largest bump on the back of your neck, with your head forward--to a point on your lower back which is horizontal with the top of your hipbones. If you find that your torso is on the border between two sizes, our experience says to go with the larger size. The hip belt should wrap around your hips, not your waist (or stomach) and the lumbar pad should be centred properly into your lumbar area. You want a significant amount of the pack's weight on your hips. A good way to do that is to make sure your hipbone is centred under your belt (and the lumbar pad centred and pressing firmly into you lower back). Get a shoulder harness that doesn't get in the way when you swing your arms or have buckles that pinch your skin.