Backpacks by Hiker Questions, Answered

Torso length: why height is the wrong ruler

Nearly every brand measures the same way: from the C7 vertebra, the bony bump where the neck meets the shoulders, to the iliac crest, the top ridge of the hip bones.^2,6 Hyperlite says plainly that height is not a reliable proxy, and Kelty calls the torso number only a starting point for fit.^1,7 Mystery Ranch is the exception: it measures down to a point just behind the belly button, so its sizes do not transfer to other brands.⁸

The long-torso answer puts the cutoff at 19.5 inches. That line does not appear in the sources checked, and brand charts differ. Granite Gear's sizes run Short 15–18 in, Regular 18–21 in and Long 21–24 in, so a 19.5-inch torso is a Regular there.⁹ Hyperlite's Southwest comes in five torso sizes, from under 15 inches to 21-plus.¹⁰ Always read the specific brand's chart. If you fall between sizes, Mystery Ranch recommends sizing down so the waist belt can tighten securely on the hips.⁸

Women's fit, shoulder shape and hips

Women's packs differ mainly in shape. Deuter's SL packs use a shorter back panel, narrower S-shaped shoulder straps and conically shaped hip fins.⁶ Granite Gear builds its women's hip belts for hips with a greater angle.⁹ Gregory, by contrast, sizes identically across genders, so a medium is the same torso size whichever label it carries.² Choose by torso length and by how the straps and belt sit on you, not by the label alone.

Shoulder shape is where the wide-shoulders question really lives. ULA offers J-straps for flat or square shoulders and S-straps for standard or sloping shoulders.¹¹ For hips, ULA sizes men's belts at pant waist plus 2 inches, and adds 3 to 5 inches to a woman's smallest waist measurement depending on build.¹¹

Children: how much to carry and when to ride

The child-load answer gives age bands (under 10%, 10–15%, 15–20%) credited to outdoor programs; those bands are not in the sources checked, and the adult 20% figure it starts from is a hiking rule of thumb with no primary source. The AAP's current advice is a pack of no more than 15% of body weight.³ Nemours gives 10–20%.⁴ A research review sets children's total load at no more than 10% of body mass.¹² Deuter gives weights instead: up to 1 kg for preschoolers, 3 kg for elementary kids, 4–5 kg for under-12s and 7 kg for teens up to 16.¹³

For carriers, the key test is sitting up unassisted. CPSC describes frame carriers as intended for children who can sit upright on their own and weigh 16 to 50 lb.¹⁴ Deuter says that milestone, with good head control, usually arrives around 8–9 months, later than the six months quoted in the answer.⁵ Follow the carrier's own limits and ask your child's doctor if unsure. Recalls happen too: CPSC announced a 2016 recall of Osprey Poco AG carriers and a May 2025 recall of Deuter Kid Comfort carriers, both over fall hazards, so check any used carrier against recall lists.^15,16

Knees and descents: what poles do and don't do

For hikers worried about joints, poles have solid evidence on the way down. On a 25-degree downhill ramp, poles cut knee compressive and shear forces by 12–25%.¹⁷ Another study found the downhill benefit held with no pack, a day pack and a heavy expedition pack.¹⁸ On level ground the picture changes: even pushing much harder on the poles did not lower knee compression.¹⁹