By Dana Okoro, Editorial Reviewer · Published September 14, 2026, 6:03 PM ET · Updated September 29, 2026, 6:16 PM ET
Direct Answer
Fitting a hiking backpack starts with measuring torso length and hip size to pick the correct frame and hipbelt size, then loading the pack with realistic weight and adjusting the straps in order: hipbelt first, shoulder straps next, then load lifters and sternum strap. A correct fit puts most of the load on the hips, not the shoulders.
In plain English
Fitting a backpack has two parts. First you pick the right size, using two body measurements: the length of your back and the distance around your hips. Then you put some weight in the pack and adjust the straps so it sits well on your body.
Weight matters because an empty pack hangs differently from a full one, the same way a coat feels different with heavy things in its pockets. Put in some real gear or a few water bottles before you start.
Then work from the bottom up. Tighten the padded hip belt around the top of your hip bones first. Next snug the shoulder straps, then the two small straps above your shoulders, and finally the strap across your chest. Done in that order, most of the weight rests on your hips and legs, which are much better at carrying it than your shoulders.
Fitting a hiking backpack is a two-part process: choosing the correct size using body measurements, then adjusting a loaded pack's straps so the fit actually works on the trail.
Step 1: Measure before choosing a size
Torso length — measured from the C7 vertebra at the base of the neck to the iliac-crest line at the top of the hip bones with a flexible tape measure — determines frame size. Hip circumference, measured around the same iliac-crest landmark, determines hipbelt size. Both numbers are compared against the specific pack's own chart, since size labels vary between brands.
Step 2: Load the pack before adjusting it
An empty pack fits differently than a loaded one, since weight changes how the frame sits against the back. Fill the pack with something close to a real trail load — Big Agnes suggests 10 to 20 pounds, enough to reveal fit problems — before making any strap adjustments.
Step 3: Adjust in the correct order
Hipbelt first. Center the belt over the hip bones and tighten until it carries the pack's weight without shifting.
Shoulder straps second. Snug them so they wrap the shoulders without gaps, without taking over load the hipbelt should be carrying.
Load lifters third. These small straps above the shoulders should pull at roughly a 45-degree angle from the pack to the shoulder, angling the load in toward the back.
Sternum strap last. Positioned an inch or two below the collarbone, tightened just enough to keep the shoulder straps from sliding outward.
Working through how to adjust a hiking backpack's straps in this order, rather than randomly, is what turns a correctly sized pack into a comfortable one — a pack that's the right size but poorly adjusted can still hurt.
Signs the fit is off
Shoulder pain often means the hipbelt isn't carrying its share of the load, and lower-back pain can point to a frame that's too long or too short for the measured torso length. Both are reasons to re-check the measurement before assuming a different pack model is needed.
Why the hips should do the heavy work
The hip-first order is built on how the body tolerates pressure. A PLoS One study found the hip region tolerates pack pressure significantly better than the shoulder region, and that static strap force predicts discomfort; the authors recommend moving load from shoulders to hips wherever possible.1 A load-carriage review in Military Medicine likewise says hip belts should be used whenever possible because they reduce shoulder pressure and increase comfort.2
How much the hips actually take is contested. Big Agnes aims for about 80%,3 Alpkit says 60 to 80%,4 and the US Army's foot-march manual reports about 30% on the hips and 70% on the shoulders with a frame and hip belt.5 The direction of the advice is consistent even though the numbers are not.
Test load and strap details from the fit guides
Big Agnes recommends fitting a pack with 10 to 20 pounds loaded,3 which is enough to see how the frame settles. For the belt, Deuter says to center the hip fins over the top of the hip bone before securing the waist belt,6 and Kelty says the middle of the belt padding should rest on the iliac crest.7
For shoulder straps, Deuter warns against over-tightening because the waist belt should carry the main load.6 Kelty describes a good shoulder fit as straps that run over the shoulders and just begin to angle down toward the pack.7 Load-lifter angle advice ranges from 45 degrees (Big Agnes) to 30 to 45 (Deuter) and 25 to 45 degrees from horizontal (Alpkit).3,6,4 For the chest strap, Alpkit says about an inch below the collarbone.4
Reading the warning signs
Gossamer Gear notes that shoulder straps set too high can pinch the neck, while straps set too low reduce weight transfer to the hip belt,8 which is often the real reason behind the shoulder pain this page describes. The page's link between lower-back pain and a wrong frame length is plausible but is not backed by a verified source, so treat it as one possibility to check rather than a diagnosis.
Some symptoms deserve more than a strap tweak. Rucksack palsy, a nerve problem from shoulder-strap pressure, is listed among common injuries from prolonged load carriage.2 Numbness or tingling in the arms or hands, or pain that persists after the pack is off, is a reason to see a doctor. Kelty also reminds buyers that a torso measurement is only a starting point for fit.7
