How to Choose a Backpacking Backpack | Fit First, Then Volume

Choosing a backpacking backpack starts with torso length and hip fit, then capacity, then features.

The right backpacking backpack doesn’t start with looks or brand. It starts with your body. Measure your torso length first because that single number decides whether the pack carries weight on your hips or drags on your shoulders. After fit comes volume based on trip length, then the features that actually matter to you. Here’s the order that works.

Why Torso Length Matters More Than Height

Torso length, not overall height, determines backpack fit. REI states torso length “matters most” when sizing a pack. The distance runs from the C7 vertebra at the base of your neck to the iliac crest at the top of your hip bones.

To measure it yourself:

• Tilt your head forward and find the C7 vertebra — the bony bump where your neck meets your shoulders.
• Place your hands on your hips with fingers forward; your thumbs rest on the iliac crest.
• Measure between those two points with a flexible tape.

Small, medium, and large sizes are not standardized across brands, so always use the maker’s own sizing chart after measuring. A medium in one brand may fit like a large in another.

Hip Belt Fit and Load Transfer

The hip belt does the heavy lifting, so it must sit correctly. Position it so the padding wraps snugly over the top of your hip bones, not above them on soft tissue.

When the pack is loaded, roughly 80% of the weight should ride on your hips and about 20% on your shoulders. Shoulder straps should sit flush against your shoulders, with load lifters angling back at roughly 45 degrees. Frame packs make this transfer possible — once your carried load passes about 15–20 lb, a frame is generally worth having because it shifts weight from shoulders to hips.

Capacity: Match Volume to Trip Length

Most backpacking packs start around 45 liters and go up to 80 liters, per REI. Popular Mechanics offers a practical breakdown:

Ultralight hikers can sometimes manage 30 liters for 1–3 nights by trimming gear weight and bulk dramatically. Before choosing volume, weigh your actual gear and account for how much space it takes, not just how heavy it is.

Features Worth Considering

Once fit and capacity are settled, features come last. REI and the Appalachian Mountain Club point to the same trio: capacity, fit, and features. Ask yourself what you’ll actually use. Pockets help organize small items, sleeping bag compartments keep your bag accessible, rain covers protect gear in wet weather, and removable day packs work well for base-camp trips. Pick only the options that meet your needs — extra weight and complexity aren’t worth it otherwise.

Test the pack loaded before buying. GearLab recommends testing with your own gear when possible, and the Washington Trails Association suggests loading about 15 pounds for a meaningful fit check. Most common mistakes trace back to skipping this step: buying by clothing size, testing an empty pack, or ignoring the gap between stated volume and real-world carrying comfort.

When you’re ready to compare affordable options that still fit well, our roundup of the best budget backpacking packs covers tested picks under realistic trail conditions.