How to Choose the Right Backpack for Hiking? | Fit Matters More Than Size

A hiking backpack fits correctly when its hip belt carries the load on your hip bones, not your shoulders.

Choosing the right backpack for hiking comes down to torso length and hip-belt fit, not your height or the pack’s liter capacity alone. A pack that matches your body transfers weight to your hips, keeps you comfortable on trail, and prevents the sore shoulders and chafing that ruin trips. Here’s how to measure yourself, pick the capacity, and dial in the fit.

Measure Your Torso Length, Not Your Height

Torso length decides which pack size fits you, and it has little to do with how tall you are. A 6-foot hiker with a short torso may need a smaller frame than a 5-foot-4 hiker with a long one.

To measure your torso length, you need two landmarks on your body:

• C7 vertebra — the prominent bone at the base of your neck where it meets your shoulders. Tilt your head forward and feel for the bump that sticks out most.
• Iliac crest — the top edge of your hip bones, felt on the sides just below your waist.

Have someone measure the distance between those two points along your spine. That number, in inches, is your torso length. Osprey’s fitting guidance notes that the hip belt should sit centered on your hip bones, not around your waist, so you’ll measure the same iliac crest for both torso length and hip belt. Match your measurement to the manufacturer’s size chart — every brand builds packs slightly differently, so check the chart for the model you want.

Pick Capacity by Trip Length

Pack capacity, measured in liters, follows how long you’ll be out and how much gear you carry. REI’s expert advice ties capacity to trip length and bulk; a week-long trek needs more volume than a few hours on a local trail.

The common capacity bands used by outfitters help narrow your choice:

• 15–30 L for day hikes with a few layers, lunch, and water.
• 30–50 L for weekend trips with a sleeping bag and shelter.
• 50–70 L for multi-day treks carrying a tent, stove, and food.
• 70 L+ for extended expeditions or winter gear.

Remember that bulk matters as much as weight. A bulky sleeping bag needs more liters than a compressed one, so size for your actual gear, not just trip days.

Fit the Pack With Weight In It

Put on a loaded pack and adjust it the same way every time. Osprey recommends loading the pack with 10–20 lb of gear before fitting, so it behaves like it will on trail. An empty pack tells you nothing about how it rides when full.

Follow this order when fitting:

1. Loosen every strap — hip belt, shoulder straps, and load lifters — before putting the pack on.
2. Center the hip belt over your iliac crest, the top of your hip bones. Tighten it snugly first; this is where most of the load should sit.
3. Tighten the shoulder straps so the pack sits close to your back without restricting breathing. You should feel minimal weight on your shoulders — Osprey’s guidance says over-tightening shoulder straps shifts load off your hips and onto your shoulders, which defeats the design.
4. Tighten the load lifters — the straps that angle from the top of the shoulder straps to the pack — until they sit at roughly a 45-degree angle to pull the pack toward your body.
5. Set the sternum strap so it feels stable across your chest without compressing your breathing. Osprey notes the top chest strap should sit about 1–2 inches below your collarbone.

A well-fit harness should also terminate about 2–3 inches beneath your armpit, per Osprey’s sizing guidance. If the straps dig into your armpits or the frame sits too high or low, try another size.

Once everything is snug, check that the hip belt sits fully on your hip bones, not your stomach or lower back. A pack that is too large lets the belt slide down, creating gaps and poor weight transfer that cause discomfort on trail.

Common Sizing Mistakes to Avoid

Most hikers pick the wrong pack by skipping the torso measurement. Choosing by height alone fails because torso length varies widely at any height. Measuring your waist instead of your hip bones for the hip belt also throws off the fit — the belt should wrap the iliac crest, not the natural waist.

Another frequent error is buying too large a pack so the hip belt sits on the stomach or lower back. And fitting an empty pack only guarantees a poor fit when it’s full; load it with weight before adjusting.

When you’ve found your size and a fit that transfers weight to your hips, you’re ready for the trail. If your hiking setup includes keeping food or drinks cold on longer trips, our roundup of the best backpacks with an insulated compartment covers models with built-in cooling for perishables.