How to Choose a Backpack: A Complete Sizing and Buying Guide
The wrong backpack can ruin a trip faster than almost any other piece of gear. Sore shoulders, hot spots on your hips, a pack that shifts around with every step, none of it has anything to do with how tough you are and everything to do with fit and sizing. The right backpack, on the other hand, practically disappears on your back.
This guide walks through everything that actually matters: what type of pack you need, how to measure yourself correctly, what size to buy, and how to pack and adjust it once you've got it.
What Type of Backpack Do You Need?
Before sizing matters at all, figure out what kind of trip you're actually packing for. Backpacks are built differently depending on how long you're out and how much you're carrying.
- Day hiking and hydration packs. Lightweight, minimal packs built to carry water, snacks, and a few essentials. Teton's Oasis 18L and 22L and the Trail Runner 2L fall into this category, built for quick trips where you want water on your back and nothing weighing you down.
- Overnight and weekend packs. Enough room for a night or two out, room for a sleeping bag, extra layers, and food without the bulk of a full multi-day pack. The Nanda 30L, Nanda 40L, and Numa 30L are built for this range.
- Multi-day backpacking packs. Built to carry everything you need for several days or more, tent, sleeping system, food, and layers, with a suspension system designed to handle real weight comfortably. The Scout, Explorer, and Signal packs are built for this kind of trip.
Once you know which category fits your trip, sizing gets a lot more straightforward.
How to Measure Your Torso for a Backpack
Here's the part almost everyone gets wrong: backpack sizing is based on your torso length, not your height. Two people who are both 5'10" can need completely different pack sizes depending on how their torso is proportioned.
Here's how to measure it yourself:
- Find the bump at the base of your neck. Tilt your head forward and feel for the bony bump where your neck meets your shoulders. That's your starting point.
- Find the top of your hips. Place your hands on your hips with your thumbs pointing toward your spine. Where your thumbs meet your lower back is your ending point.
- Measure the distance between the two points. Have someone measure straight down your back from the bump at your neck to that spot on your lower back. That's your torso length.
Most backpack sizing charts (small, medium, large, or specific inch ranges) are based on this number, not on how tall you are. If you skip this step and size a pack based on height alone, you'll likely end up with a pack that doesn't sit right no matter how you adjust the straps.
How to Choose the Right Backpack Size (By Liters)
Once you know your torso length and pack type, the next decision is capacity, measured in liters. Here's a general guide for how much space you actually need:
|
Capacity |
Best For |
What It Fits |
Teton Packs |
|
15-25L |
Day hikes |
Water, snacks, a layer, and small essentials |
Oasis, Trail Runner |
|
30-45L |
Overnight and weekend trips |
A sleeping bag, a change of clothes, food for a day or two, and basic cooking gear |
Nanda, Numa |
|
50-70L+ |
Multi-day backpacking |
A multi-night tent, sleeping system, several days of food, and extra layers |
Scout, Explorer, Signal |
If you're between two sizes, think about how you pack. Someone who packs light might do fine with a smaller multi-day pack, while someone who brings more gear or camps in colder conditions might want to size up even for a shorter trip.
Key Features to Look For
- Not all backpacks in the same size range are built the same. A few features make a real difference in comfort and usability.
- Hip belt. A padded, adjustable hip belt shifts weight off your shoulders and onto your hips, where your body can carry it much more comfortably over long distances. This matters more as pack size and weight go up.
- Adjustable fit. Some packs let you fine-tune the fit even after you've picked a size, which helps you dial things in even more.
- Ventilation. A back panel that keeps air moving between the pack and your back makes a real difference on warm days or long climbs.
- Hydration compatibility. A sleeve for a hydration bladder, plus a port for the hose, keeps water easily accessible without digging through your pack.
- Pocket placement. Side pockets for water bottles, a hip belt pocket for snacks or a phone, and a top pocket for small items you need quickly all add up to a pack that's easier to actually use on the trail.
How to Pack a Backpack the Right Way
- Heavy items in the middle, close to your back. This keeps the pack stable and prevents it from pulling you backward.
- Sleeping bag and rarely used items at the bottom. These are things you won't need until you make camp, so they can sit at the bottom out of the way.
- Mid-weight items around the heavy core. Food, cooking gear, and extra clothing layers fill in around the center.
- Frequently used items on top or in outer pockets. Rain gear, a map, snacks, and anything you might need mid-hike should be easy to grab without unpacking everything else.
- Distribute weight evenly side to side. An unevenly loaded pack will pull to one side and throw off your balance over a long day.
How to Fit and Adjust a Backpack Once You're Wearing It
Even the right size pack needs to be adjusted correctly every time you put it on. Here's the order that actually works:
- Loosen everything first. Start with all straps loose so you're adjusting from a clean baseline.
- Fasten and tighten the hip belt first. The belt should sit right on top of your hip bones, not around your waist. Most of the pack's weight should rest here, not on your shoulders.
- Tighten the shoulder straps. They should sit snugly without digging in, close enough that the pack doesn't sag away from your back.
- Adjust the small straps near the top of your shoulders. These pull the pack in closer to your body. They shouldn't be pulled too tight or left too loose, just enough to bring the pack snug against your back.
- Clip the chest strap. This keeps the shoulder straps from sliding outward and adds stability, especially on uneven terrain.
If a pack still feels off after these adjustments, it's usually a sign the torso size itself is wrong, not a strap adjustment problem.
Final Thoughts
Choosing the right backpack comes down to matching the pack to the trip, sizing it to your actual torso length rather than your height, and taking the time to load and adjust it properly once you're out the door. Get those three things right and a backpack stops being something you notice and just becomes part of how you move.
Whether you need something light for a day hike, room for a weekend away, or a pack built to carry everything for days at a time, Teton's backpacks are built to be comfortable, dependable, and easy to load up and go, no matter how far you're headed.