One of the questions we invariably get for backpacking trips is “what size backpack do I need?” It’s one of those both critical questions to ask and also an impossible question to answer. I’ll try to explain why below.
The question “what size should my backpack be?” is a little like asking me “what size tent you should bring?“The best I can do is offer some information that might be useful in helping you answer the question yourself.
Because there is such a large degree of subjectivity in the answer.
What you need is a backpack that will fit all your gear, that carries well for you, and isn’t too large that you end up filling it needlessly with gear you might not otherwise bring.
So perhaps the best place to start is assess all the rest of your trip backpacking gear. Assemble all your gear as if you’re packing for the trip. Include space for food (typically one BV 500, size 8.7 in. dia. (22.1cm) x 12.7 in. (32.3cm) height. Add in a little extra space for extra group gear such as a stove or fuel can, or whatever. Remember you’re probably going to add another item or three before you go. That’s how big your pack should be.
Since so many people have backpacked primarily 2-4 day night trips, and have very little experience with 7-12 day trips, it’s quite probable that your pack is a little on the small side for a long trip (like the majority of ours tend to be). That may mean you need to shop for a new backpack. Here’s a long article on what to look for in a backpack.
As a general rule I’m not a fan on having to carry gear outside your pack strapped or lashed to the outside. Doing so is a recipe for losing your gear (as anyone who’s bushwhacked through Alaska alder and willow can tell you). So you want virtually everything to fit inside your pack. All the time.
That means what type of tent you’re bringing matters. What sleeping bag you have, what pad you have, what you’re bringing for clothing and stayting warm, cookware, mess kits, etc. Those things, particularly the first few above, vary tremendously in size and bulk (usually inversely with weight and cost). I typically fit my sleeping bag, my sleeping bad, and virtually all my clothing in the bottom compartment of my pack. My sleeping bag stuffs down to a small size, my pad the same way; and I have a fairly efficient clothing system that works for me.
Your system may not be as compact. Or it may be more compact.
For most folks I’d recommend a 65L pack, minimum, for an adult on any Alaska backpacking trip longer than 5 days. A shorter trip you MIGHT get away with a smaller pack. But remember most of those bulky items will be consistent trip to trip, whether it’s a 4 day trip or a 10 day trip. Food and fuel tend to be the variables.
We’ve had folks come out for an 11-12 day trip with a very minimalist rig and carry a 45L pack, comfortably fitting all their gear. But someone with a good setup like that is probably NOT unsure about what pack to bring. They have their gear and their systems in place and it’s all dialled. They’re not likely to be asking me what size pack they need. So as a general rule, that size backpack will not work for you. It certainly doesn’t work for me or any of the guides in our little crew.
Obviously there’s some wiggle room here. If you’re coming as a couple or group, you might be able to share items such as a tent, etc and not need exactly 65L of backpack for yourself. Or you might have a cheaper bulkier sleeping system that requires larger a backpack to fit it. Those variables all matter more than the number I listed above. But as a general rule, you need a large backpack if you’re going out into the backcountry for a 7-10 day backpacking trip.
Remember .. get your backpacking gear system together FIRST. Your backpack accomodates that, not the other way around.