A backpack is, naturally, essential equipment for backpacking. Choosing a backpack is very personal. The best way to find one that will be comfortable for you is to try on a bunch of options in person and compare them.
If possible, you should buy your pack last, after all your other gear. This will help you determine what size pack you need to carry all your stuff.
The most important thing to get right when buying your pack is the fit. Packs come in different sizes, and you want one that’s well-matched to the length of your torso. Check out REI’s excellent video guide to measuring your torso length.
A well-fitting pack will help you comfortably carry your gear on long hikes. A poorly-fitting one will quickly make your heavy load uncomfortable, and can hamper your balance and even lead to injury. For this reason, a pack is probably the most important large piece of gear that you should strongly consider purchasing for yourself rather than borrowing from a friend. A borrowed tent or sleeping bag will probably work fine for your first trip, but if you borrow a pack that doesn’t fit you well, you’ll be in for a rough time. This is especially true on demanding hikes like the Enchantments, where you’ll be traveling a long way and up significant elevation.
The more gear you’re planning to hike with, the bigger a pack you’ll need to fit it all. Here’s a popular backpacker technique for determining what size pack is right for you.
First, collect all the gear you intend to carry. If you haven’t bought all your gear yet, find some household items that can fill in for now (couch pillows or a rolled up towel work well as substitutes for a tent or sleeping bag, for example).
Next, find a big cardboard box. It should be big enough to easily fit everything you plan to carry.
Put everything into the box, minimizing the amount of dead airspace and trying to keep the top surface of all the stuff pretty level.
Measure the length and width of the box, and the depth of the stuff that’s in it. Multiply these together to get the volume of your gear. If you measured in inches, you’ve now got the volume in cubic inches. Most backpacks advertise their capacity in liters (there are 61 cubic inches per liter; to convert from cubic inches, divide by 61).
Next, weigh all your stuff. Put the box on your bathroom scale and note the number. Then empty the box and subtract the weight of the empty box to find your total gear weight.
Now you know the volume of pack that you need, and the weight you’ll be carrying. Write these two numbers down, and keep them in mind when you’re shopping for packs.
Some packs are basically just a single big top-loading sack with shoulder straps sewn on. Others have dozens of zippered pockets, built-in hydration bladders, and detachable “brain” compartments that transform into daypacks.
These extra features can be convenient, but they also add a lot of weight. The difference in weight between a minimalist pack and an ultra-featurefull one can be two or three pounds—that’s as much as a whole extra tent! Consider which features you’ll actually want in a pack, and try to find one that only has those features and not a lot of extra stuff that you won’t use.
Backpack fit is very personal. With so many options on the market, we don’t feel comfortable recommending any particular backpack as “the best”, even within a specific capacity range or set of features. All of the major brands (REI Co-op, Osprey, Gregory, Kelty, Deuter, etc) make solid options, and any would make a great first backpacking pack.
We recommend that you visit your local outdoor outfitter and try on a bunch of packs in person to see which feels good to you. Most outdoor retailers will have a whole department devoted to backpacks, with staff that can help you determine the right fit and beanbags to load up packs with so you can walk around the store carrying a realistic weight.
Keep the volume and weight of your gear in mind while you’re shopping, and remember that extra features on a pack add a lot of weight. But most importantly, make sure your pack is comfortable to wear when it’s loaded.