Torso size: how to measure it and match a bag

The hook

When a loaded bag drags at your shoulders, the cause may be its length against your torso, not its weight. Torso length is the first fit measurement to take for a pack you plan to load.

What is it

Torso length is measured from the C7 vertebra (the prominent bone at the base of the neck) to the iliac crest (the top of the hip bones). It tells you which bag size fits your back. Bags come in small (typically 41 to 46 cm, or 16 to 18 in), medium (46 to 51 cm, or 18 to 20 in) and large (51 cm and up, or 20 in and up) torso lengths, sometimes with an adjustable harness that covers a range. Bags sold as women's usually run shorter and curve the straps differently, but the measurement is what counts; women's backpacks covers the overlap.

Why it matters

A bag too long for your torso sits on your tailbone rather than your hips and leaves the weight on your shoulders. A bag too short doesn't meet the hip belt at the right point, so the belt can't take load. Either mismatch can feel like a heavy bag when the bag is the wrong length for your body. How a hip belt takes weight depends on this fit.

How to spot it

Measure your torso with a helper and a soft tape. Stand straight and tilt your head forward to find C7, the bony bump at the base of your neck. Put your hands on your hips, thumbs pointing back, with your fingers on top of your hip bones. Your helper measures down your spine from C7 to the line between your thumbs. Compare that to the bag's torso size range, and on an adjustable harness check that the range covers your measurement. Then try the bag on: the hip belt should sit centered on your iliac crest, not on your waist or below. Torso length is only part of fit; bag shape is the rest.

When you don't need it

Small bags (under 10 L), slings and light EDC bags don't rely on load transfer, so torso length matters less. As a rough guide, under about 7 kg (15 lb) carried for short periods, fit precision matters less too.