How to Choose a Backpacking Backpack | Fit Before You Buy

Choose a backpacking backpack by matching its volume to your trip length, then sizing it to your torso and hips before testing it with real weight.

Choosing a backpacking backpack comes down to three steps: estimate the liters you need for your trips, measure your torso length and hip circumference, then load the pack with roughly 15 pounds and adjust the straps to confirm the weight settles on your hips. Most packs start around 45 liters and range up to 80, but the right number depends on your gear, not a generic chart.

Start With Volume, Not Features

The single biggest mistake is buying a pack before you know how much space your gear actually takes up. REI notes most backpacking packs run from about 45 to 80 liters, while the Appalachian Mountain Club points to optimal volume, body size, and optional features as the three variables that matter.

Use your trip length as the first filter. Lowe Alpine’s guidance breaks it down this way:

• Day hikes: 18–40 liters
• Multi-day hiking: 35–50 liters
• Multi-day trekking: 40–60 liters
• Remote multi-day trekking: 60–120 liters

CleverHiker’s benchmark lands similarly: about 40 liters for 1–3 nights and 60 liters for 4–6 nights. The shared conclusion across all of them is simple — choose the lightest pack that can carry your gear, not the biggest one on the shelf. Pockets, sleeping-bag compartments, rain covers, and removable day packs are refinements worth considering, but only after volume and fit are solved.

Measure Your Torso, Not Your Height

Torso length, not height or clothing size, determines whether a pack fits. The standard measurement runs from the C7 vertebra — the bony bump at the base of your neck — down to the line between the tops of your hip bones.

Have someone help you measure, because reaching behind your own neck makes the tape drift. Run the measuring tape straight down your spine, not along its curve. Once you have that number, use the brand’s sizing chart to pick your size. Sizing is not interchangeable between brands — one company’s medium is another’s large, so always check the chart for the specific pack you’re considering.

Test The Fit With Real Weight

An empty pack tells you almost nothing. Load it with about 15 pounds, loosen every strap, and put it on. Adjust in this order:

1. Hip belt first. It should hug the top of your hip bones — not sit above them or slide below them.
2. Cinch the waist belt just above the hip bones so the belt carries the bulk of the load.
3. Tighten the shoulder straps until they rest comfortably without bearing heavy weight.
4. Snug the load-lifter straps — the ones running from the top of the shoulder straps to the pack — to pull the load closer to your back.

When the adjustment is right, the weight should feel anchored on your hips, with your shoulders free to move. If the pack still drags on your shoulders, the torso length is wrong for you.

Load It The Way You’ll Carry It

Once the pack fits, loading matters almost as much. Stow the heaviest items — water, stove, fuel — closest to your back and toward the middle of your torso. That keeps the center of gravity stable and lets the hip belt and load lifters do their job instead of fighting a shifting pack.

Frame choice follows load. Once your trip weight passes about 15–20 pounds including food and water, a framed pack is the right call because it transfers weight from your shoulders to your hips. REI’s grouping is a useful shorthand: ultralight loads run 10–30 pounds, standard loads 20–40, and heavyweight expedition loads 40 to 70-plus.

If you carry consistently heavy loads or have existing neck or back pain, that’s a strong reason to prioritize load transfer over a lighter pack. And when you’re ready to buy, covers a practical pick for everyday carry.

REI’s full backpacking pack buying guide walks through sizing charts and adjustment details for specific brands. The bottom line: every official guide lands on the same sequence — measure your torso, size the hip belt, and test with real weight before you commit.