How to Measure Your Torso for a Hiking Backpack (Step-by-Step Fitting Guide)
You already know your height. It is on your license, your job application, and maybe still marked on a doorframe somewhere from when you were twelve. That number tells you almost nothing about which backpack size will actually fit you.
Two hikers who are both exactly six feet tall can need two completely different frame sizes. The pack you grab off the shelf based on height alone might be wrong before you even try it on.
The number that actually matters is your torso length. Learning how to measure your torso for a hiking backpack takes about a two-minute session with a flexible tape measure and a little patience. Get it right, and a mid-range pack can feel like it was built for your body specifically. Get it wrong, and even an expensive one will fight you by mile three.
TL;DR: Measuring Your Torso for a Hiking Backpack
The Height Fallacy: Why Your Stature Does Not Predict Your Backpack Size
Torso length and standing height come from different combinations of genetics and growth patterns. Two people can be the exact same height while carrying totally different proportions between their legs and their spine. One person’s height comes mostly from long legs, while another’s comes mostly from a long torso.
The correlation between height and torso length is real, but weaker than most people assume. A commonly cited shorthand among hikers estimates torso length at roughly 27% of total height, though this comes from community-shared math rather than a controlled study, and individual variation is significant enough that two people of the same height can land a full size bracket apart.
The gap between your height bracket and your true torso length regularly runs one to two inches or more. That gap is the difference between a pack that disappears on your back and one you are still adjusting at the trailhead an hour in.
A six-foot-two hiker with a long-legged build might have a proportionally short torso and need a small frame. A five-foot-eight hiker with a longer trunk might land at the high end and need a medium or large. Height told you nothing useful either way.
Trail Story: Most hikers assume height and torso length move together, and the first time that assumption gets corrected is usually standing in a fitting area holding two different pack sizes with roughly the same number on the tag. The instinct is to trust the taller size because it feels safer. It rarely is.
Experienced fitters have watched plenty of tall hikers walk out with a small frame and shorter hikers walk out with a large one, and both were the right call once the actual torso number was on the table.
The Biomechanics of Fit: Why Mismatched Sizing Ruins Your Hike
A hiking backpack is essentially a machine for moving weight off your upper body. The goal is to transfer 60% to 80% of the total load down to your pelvis, the strongest, most stable structure in your body, rather than letting it sit on your shoulders and spine.
When a pack is too long for your torso, the hip belt sits too low to properly grip the top of your hip bones. Weight isolates on your tailbone instead of your hips, and the shoulder harness above it loses its job entirely. Without that upper stability, the pack sways with every step, and your body spends energy fighting the motion instead of walking.
When a pack is too short, the opposite problem shows up. The hip belt rides up and constricts your stomach instead of resting on your hip bones. Under load, a too-short frame behaves less like a rigid support and more like a column that buckles, shifting the bulk of the pack’s weight straight onto your shoulders instead of your hips.
That shoulder overload has a real mechanical cost. Narrow straps compress the brachial plexus, which is the bundle of nerves and blood vessels running through your shoulder. This is why your hands can go numb or tingle on a long climb. A poorly fitted pack also shifts your center of mass backward, so your body compensates by leaning forward to counterbalance the load, and that forward lean puts real compressive force on the discs in your spine and burns through muscle energy fast.
One thing worth being straightforward about: while the 60% to 80% load transfer target is well established, researchers do not fully agree on exactly how shifting weight between your shoulders and hips changes your metabolic cost on the trail. A systematic review of load-carriage biomechanics published in the Journal of Applied Biomechanics confirms that proper load distribution stabilizes your center of gravity and prevents local muscle fatigue, even if researchers still debate its exact impact on your raw metabolic energy cost.
Field Notes: Load lifter straps, the ones running from the top of your shoulder back to the pack, should sit at roughly a 45-degree angle.
If they point straight up or lie nearly flat, your torso length is off even if the hip belt feels fine.
Locate Your Landmarks: Finding the C7 Vertebra and the Iliac Crest
Before you can measure anything, you need to find two bones. One sits at the base of your neck. The other sits at the top of your hips. Everything else in this guide depends on locating these two points correctly.
The Upper Mark: Your C7 Vertebra
Stand up straight, then tilt your head forward and bring your chin toward your chest. Run a finger, or better, have a helper run theirs, down the back of your neck until they feel the bone that sticks out the most. That is your C7 vertebra, and it usually lines up with the collar of a standard crew neck t-shirt.
Once you have found it, lift your head back to a normal, upright position. Leaving your chin tucked down while you measure will add false length to your number, so this step matters more than it sounds like it should.
The Lower Mark: Your Iliac Crest Plane
Place your hands flat on the sides of your lower abdomen and slide them downward until you feel the top edge of your hip bones. Point your thumbs backward toward your spine and your index fingers forward, like you are framing your waist.
Have a helper draw an imaginary horizontal line across your lower back connecting your two thumbs. A validity study on manual palpation of lumbo-pelvic landmarks found the method has acceptable accuracy for general use, though with enough measurement error that precision matters, which is why the posture and layer notes below are worth following closely. That line marks your bottom measurement point, and it roughly lines up with your L3 vertebra if you want the anatomical reference.
Field Notes: Do this over a thin shirt, not a jacket or a hoodie. Bulky layers add fake inches to your reading and can push you into the wrong size bracket before you have even started.
Field Notes: On a steep climb or descent, a hip belt that is not sitting on the actual iliac crest shelf tends to reveal itself fast. It slides, it rotates, or it digs into soft tissue instead of bone.
Checking the wrap alignment after the initial fitting, with the pack loaded and on level ground first, catches sizing mistakes that a quick in-store try-on often misses.
The Measurement Process: How to Get Your Spinal Number
With both landmarks located, the actual measurement takes less than a minute. You have two options depending on whether you have a helper on hand.
If you do not have a flexible cloth tape measure, you can easily use a piece of household string or twine. Simply trace the natural curve of your spine with the string, mark the C7 and iliac plane landmarks directly on the cord, and then lay it flat on a table to measure the length with a standard rigid hardware tape measure.
If you want to watch the landmarks and measurement techniques demonstrated live, we put together a brief companion video showing both the helper and solo methods in real time.
The Helper Method
Stand fully upright with your spine in a natural, neutral posture, not slouched, not arched. Have your helper place the zero end of a flexible tape measure directly on your C7 vertebra.
The tape should run flat along your back, following the natural curve of your spine rather than being pulled taut in a straight line. Your torso length is the number on the tape exactly where it crosses the imaginary line connecting your thumbs at the iliac crest.
The Solo Method
No helper? Stand with your back against a wall. To maintain a neutral, upright spine, make sure your heels, shoulder blades, and the back of your head rest lightly against the flat wall.
Mark the wall with a pencil exactly where you feel your C7 vertebra, then mark it again at the height of your iliac crest line. Holding a hardback book flat against your head or hips can help you keep your markings perfectly level. Once marked, step away and measure the straight-line distance between the two pencil marks.
A quick sanity check: when your arms hang naturally at your sides, your elbows usually land close to the level of your iliac crest. If your two pencil marks and your elbow height are wildly different, remeasure before you trust the number.
Three mistakes show up constantly. A rigid metal tape measure cannot contour to the curve of your spine and will read short. Leaving your head tilted down after finding C7 adds false inches. And letting the imaginary thumb line droop instead of staying level can throw off the whole number. None of these are hard to avoid once you know to watch for them.
Field Notes: Skip the metal tape measure from your toolbox. It cannot bend around the curve of your spine and will shortchange your number by an inch or more. A cloth sewing tape or a piece of string and a ruler works better.
Sizing Systems Decoded: Matching Your Torso Number to Brand Sizing Charts
Once you have your number, matching it to an actual pack means learning to read the brand’s chart, and every brand approaches this a little differently.
Gregory Sizing
Gregory builds its sizing around torso length alone, for everyone. The brand’s own position is straightforward: a medium is a medium, whether it is a men’s or women’s pack. Women’s specific Gregory packs use the identical torso length charts as the men’s versions, with the gender-specific design changes limited to the shape of the shoulder straps and hip belt, not the frame sizing itself.
Gregory typically offers double sizes with continuous adjustability, like an SM/MD that covers 15 to 19 inches or a MD/LG that covers 18 to 22 inches. Expedition packs like the Baltoro instead use fixed sizes: small runs 15 to 17 inches, medium runs 17 to 19, and large runs 19 to 21.
Osprey Sizing
Osprey takes the opposite approach, building gender-differentiated frames with overlapping adjustable harnesses. On the men’s Aether, for example, an S/M covers roughly 17 to 20.5 inches, and an L/XL covers 19.5 to 23 inches. Women’s specific packs like the Ariel run smaller across the board, with an XS/S covering 13.5 to 17 inches and an M/L covering 16 to 19.5 inches.
Deuter Sizing Profiles
Deuter skips the S/M/L labels almost entirely and sorts packs into three body profiles instead. Regular is built for an average frame around 18 inches. Slim Line is proportioned for shorter torsos around 16.5 inches, with narrower strap spacing and a conically shaped hip belt. Extra Long adds roughly 2.3 to 3.5 inches on top of the regular profile for taller hikers.
Deuter’s adjustable VariSlide and VariQuick suspensions then stretch across a wide range, from about 16.5 up to 24.4 inches, so the profile gets you close and the adjustment dials in the rest.
The Golden Rules for Borderline Measurements
If your number lands exactly between two sizes, the standard rule for most brands is to size down. This keeps the frame slightly shorter so the hip belt remains anchored securely on your iliac crest shelf, preventing the pack from riding up under load.
This standard holds true for Gregory packs as well, despite their micro-adjustable suspensions. Gregory officially advises caught-between hikers to size down to keep the load lifter angles correct, unless you have an exceptionally broad or stocky frame. In that specific case, size up to ensure the harness padding wraps around your shoulders comfortably.
There are two other real exceptions. Heavy-load hauling frames, the kind built for multi-day trips with serious weight, often benefit from sizing up, since the extra length improves the geometry of the load lifter straps at high loads. Frameless packs are the other exception. Because they have no rigid support to keep their shape, sizing up helps ensure the pack is long enough to actually reach your pelvis in the first place.
If you are still deciding between pack types and capacities, our hiking backpack fit and selection guide walks through frame types and the rest of the picture beyond torso length alone.
Editor’s Notes: None of this is complicated, but it does reward a little patience. Rushing the landmark-finding step is the most common reason a measurement ends up off by an inch, and that one inch is often the difference between a pack that disappears on your back and one you are adjusting all day. Take the extra sixty seconds. Future you, six miles in, will not regret it.
Measure Once, Hike Comfortably
Two minutes with a tape measure and a willing helper is a small trade for a pack that actually fits the body you have, not the height on your license. Find your landmarks, measure along your spine, and use the brand chart that matches whatever model you are eyeing.
Once you have your torso length locked in, the rest of choosing a pack gets a lot easier. If you want to see how that number plays into the bigger picture, our beginner’s guide to hiking backpacks covers frame types, capacity, and the features actually worth paying for.
What is your torso number, and did it match what you expected based on your height? Tell me in the comments. I read them, and it helps me know what to cover next.
Founder & Gear Research Editor
Sonia Zannoni
I’m Sonia, the founder and Gear Research Editor behind Best Trail Backpacks. I research hiking backpacks through a comfort-first lens, with a focus on fit, back pain, ventilation, practical trail use, and the small design details that can make or break a hike.
I do not pretend to personally test every backpack I cover. Instead, I compare manufacturer specifications, product details, verified buyer patterns, and practical fit guidance to help casual hikers make better buying decisions without getting buried in gear jargon.
My goal is simple: help you choose a backpack that fits your body, your trail plans, and your budget, without the usual overwhelm.
About the Founder
