What are Backpacks for?

The objective of a backpack is to get your gear from here to there and back in something that is reliable and comfortable.

A backpack is one piece of gear that I would not recommend you rush off and buy.  A new one can be relatively expensive and, with all the different styles and sizes, you could end up with one you might be unhappy with.  Try borrowing one at first one—or several of different styles and sizes—to get a feel for what is right for you.  Obviously, if you buy the pack, you aren't exactly stuck with it.  But realize that when you resell it, it will probably be at a substantial discount.  So, my advice is to first gain experience regarding what you like and need before you take the fiscal plunge.

Alternatively, for a starter, consider buying a good quality used pack from someone who has outgrown, upgraded, or no longer uses theirs.  Be careful though, to not get a pack that is too dated because pack technology has advanced quite a bit in the last few years, especially with regard to straps that increase comfort and help control your load.  Many older packs, for example, don't have sternum straps, load control straps, compression straps, and integrated water bottle holders, etc.  Some don't even have a padded hip belt!

With that in mind, most of the following observations for buying a pack are also applicable to renting or borrowing one.

The objective is to get your gear from here to there and back in something that is reliable and comfortable.  The big choice to make is whether to buy an external (left photo) or internal (right photo) frame pack, although that decision is becoming less important these days.  Internal and external frame pack designs seem to be converging, with external frames sometimes taking on nearly the same profile as internal frames—tall and narrow with a bottom (sleeping bag) and internal frame adding many external pockets and places (web daisy chains and lash points) to hang things off the top, sides and front outside of the pack—areas where external frames have traditionally excelled.  External frames have also become more flexible (using materials other than steel or aluminum).  Both have added mechanisms to adjust position, a feature first found only on a few external frames.  General purpose external and internal frame packs have also merged functionally (specialized climbing and "contour" packs are exceptions) and it is now difficult to distinguish some an internal frame packs from external frame.  For this reason, focus on function, not style, when looking at backpacks.  However, if you still want to make a fashion statement, you can do it with a $1,000.00 custom-made, neon-pink, space-aged cloth pack with carbon fiber stays, heat-treated titanium frame, carboplast buckles, and silk-lined shoulder straps! As for the rest of us, we'll settle for a functional pack and use the rest of the money to go on an backpacking adventure!

What to Look for

I researched loads of web sites for data on selecting a pack and have assembled some what seems to be the prevailing wisdom:

Fit & Adjustability

It fits your build now—and later.  Adjustability is particularly important for novices who haven't quite figured out how to make a pack comfortable or who may change height or weight (e.g., a still growing Scout).  Check the range of adjustments for torso length (shoulder straps and/or hip belt adjustment) to ensure the distance between them can be changed.  Try not to be at the outer end (high or low) of the range of adjustment.  You'll likely to be most comfortable if you fit somewhere close to the midpoint of the adjustment range.  All packs are different and manufactures use different measurements to distinguish between "small," "medium," and "large" (there is no industry standard) or between "adult" and "junior (Scout)" size.  In general, however, if you are shorter than 5'4" you may want to check out "small" sizes first.  A "medium" may be your size if your height is between 5'2" and 6'0".  If you're taller than 5'10", look at "large" sizes.  For a more precise fit look to the pack manufacturer's stated "torso length" range.  What is torso length, you ask? The experts say that if you run your hand down the back of your neck until you feel a lump very near the top of your shoulders (generally about the 7th vertebra) and measure down to the top of your pelvis (hip crest), you'll have your approximate torso length.  Start then, by choosing a pack size that has this measurement near the midpoint of its torso range that matches yours. Some manufacturers also have packs specifically designed for women and young men (e.g., the Kelty Tioga, Jr.) but as most packs are adjustable over a small range of sizes and many overlap in size ranges any small pack will generally fit a petite woman or Scout (are we getting too confusing?).  Still, there is no substitute for trying on the pack you buy (with weight in the pockets and compartments) or for borrowing one that is similar in size, construction, and manufacturer to the one you are considering buying.

Straps and belts:

Padded Shoulder Straps
These straps go from the pack just behind/below the top of the shoulder, over the shoulder, and back down to the pack somewhere near the hip belt (bottom).  When novice backpackers experience sore shoulders it is often because too much weight is being carried by the shoulders, e.g., the shoulder straps are lifting the weight off the hip belt.  There are two remedies (1) loosen the shoulder straps, and (2) change the position where the straps attach to the pack.  If loosening the straps causes the pack to "fall away from the back" and the straps attach to the pack well below your shoulders, the pack (or adjustment) may be too short for your torso length and the shoulder straps could be moved up on the pack (or moved the hip belt down).  If it "falls away" and the straps attach above your shoulders, you may need to move them down (or move the hip belt up) on the pack.  The shoulder straps should attach to the pack just below shoulder level.  Another potential remedy for the "falling away" problem is to tighten the load control straps, if the pack has them.  If problems persist and you are out of adjustments, a different pack may be necessary.
Sternum Straps
This strap goes from one shoulder strap to the other across the chest.  Not all packs have this strap, but this is one strap I find a near necessity.  This strap, when pulled tight, relieves the pressure of the shoulder straps on the arms and distributes the pressure across the chest.  When Scouts experience numbness in their arms, it can often be relieved by tightening the sternum strap.  Sternum strap retrofit kits are available and a lashing strap with a quick release buckle from one shoulder strap to the other is a potential in-the-field substitute.
Padded Hip Belt
The belt attaches to the bottom of the pack and goes around the waist.  The weight of the pack should rest on your hips, not your shoulders.  This requires that the hip belt be pulled fairly tight.  Experts contend that the shoulder straps are there primarily to keep the pack from falling backwards off of the back.
Stabilizer Straps
These straps go from the sides of the hip belt to the pack on internal frames (and some external frames).  They are needed because the "block" of padding at the bottom of the pack rests on the hips just above the tail bone.  Without them, the pack would rock from side-to-side as you walk and potentially cause instability.  By tightening these straps, the pack is restricted from side-to-side motion.
Load Control Straps
These straps extend from shoulder straps just in front of the shoulder to the top of the pack.  Not all packs have these.  When pulled tight, they pull the pack weight in close to the shoulders.  When loosened, they allow the pack to "fall off the back."  These are useful features on steep and/or rocky climbs.  Tightening them while going up hill brings the weight in closer so you don't need to bend over quite as much to maintain your balance.  Going down hill, you may want to loosened these straps somewhat so that the pack falls slightly off the back.  That way if you stumble, you fall backward against the hill rather than forward down the hill.
Compression Straps
These straps generally extend horizontally around the main compartment of the packs.  They can attach to the outer edges of the pack or the frame itself.  They serve two purposes.  First, if you have a "front-loading" pack with a zipper flap opening (like most school "book bag" packs) they relieve stress off the zipper.  It is very important that you snug them up, for with heavy firm loads, zippers can easily rupture.  Second, the straps keep the contents from shifting and help stabilize the weight.  Without compression straps, the contents of a large compartment may be loose and heavier items will settle to the bottom (generally, you want weight high and close to the shoulders).  The compression straps constrict the compartment's diameter, forcing the contents to stay higher.  Some packs may also have vertical compression straps running up and down the length of the pack.  These straps relieve the pressure off the lower (sleeping bag) compartment zipper, secure the top cover, and compress the contents down to make the pack more stable.  They sometimes are left long at the bottom so that they can double as lashing straps for securing things external to the pack.  Internal frames may have zigzag compression straps (or elasticized bungee style cords).  These packs have tall narrow profiles and the intent is to hold the contents steady, no necessarily squeezing the contents.
Load Lifting Straps
These straps are appearing on higher end internal (and a few external) frame packs to keep them from sagging and hold the pack close to the torso.  They attached to the bottom of the shoulder strap and affix to the bottom or side of the pack.  They are designed to lift and snug the lower part of the pack against the lumbar area of the back.  Don't confuse these with shoulder strap length adjustments and stabilizer straps.

Other factors to consider

How Much Do They Cost?

So, what should you pay for a pack? Junior packs may be had for as little as $75.00.  You can pay a lot more, but it probably isn't necessary for normal backpacking activity.  External frame packs tend to be cheaper than internal frames because of the extensive sewing and reinforcement necessary for internal frames to carry the same volume and weight.  At the lower price end of this range are some JanSports models.  In the intermediate range you might find Kelty, Eureka.  Gregory, and North Face.  Some Lowe models are considered premier packs—and command a premier prices—and are probably too premier for all but the most serious backpackers.  I would defer your purchase until you determine how serious you are about backpacking and have had first hand experienced with several types so you can better assess your wants and needs.  A few good sources to look at include (but certainly not limited to):

Don't buy on impulse!  Local stores offer fine selections, but prices can vary immensely so be prepared to spend some time doing price comparisons.  Stores often have special prices on last year models, floor models, and returned-for-repair items (look for ones with a guarantee).  Some examples from Fall 2008 catalogs are shown below.

Source Brand Model (cu. in.) Style Condition Price
Campmor Kelty Yukon Youth (2900) External New $89.99 (Sale)
Campmor Kelty Trekker (3950) External New $109.99 (Sale)
Campmor Kelty Super Tioga (4900) External New $139.97 (Sale)
Campmor JanSport Klamath 85 (5200) Internal New $109.99
Outdoor Outlet Lowe Alpine Appalachian (4900) Internal New $129.99 (Sale)
Outdoor Outlet Kelty Junior Tioga (2050) External New $99.99
Outdoor Outlet Kelty Yukon (2900) External New $109.99
Outdoor Outlet Kelty Trekker (3950) External New $139.99