By Dana Okoro, Editorial Reviewer · Published September 14, 2026, 6:03 PM ET · Updated September 29, 2026, 6:16 PM ET
Direct Answer
Torso length for a backpack is measured from the C7 vertebra at the base of the neck to the iliac-crest line at the top of the hip bones, using a flexible tape measure run along the spine's curve while standing naturally. A helper improves accuracy. Compare the result in inches to a brand's torso-length chart, not to height.
In plain English
Torso length is the length of your back, from the base of your neck down to the top of your hips. Backpacks come in sizes based on this number, not on how tall you are, because two people of the same height can have very different back lengths.
You need two landmarks. The top one is a bump at the bottom of your neck: tip your head forward and feel for the bone that sticks out most. The bottom one is the top of your hip bones: put your hands on your hips, thumbs pointing toward your back, and your thumbs will rest on it.
Have a friend run a soft sewing tape from the neck bump down your spine to the imaginary line between your thumbs. That number, in inches or centimeters, is what you compare to a pack's size chart. It is a lot like checking your shoe size before buying shoes.
Torso length for a backpack is measured as the distance down the spine from the C7 vertebra to the iliac-crest line, using a flexible tape measure while standing in a natural, upright posture.
Finding the two landmarks
Tilt your head forward to feel for the C7 vertebra, the prominent bony bump at the base of the neck where it meets the shoulders — it stays raised even once the head is upright again. For the iliac crest, place both hands on the waist with thumbs pointing backward and slide down until the thumbs catch the top ridge of the hip bones, then picture a line connecting that ridge across the lower back.
Taking the measurement
Have a helper hold a flexible cloth or vinyl tape measure at the C7 point and run it down the curve of the spine to the iliac-crest line, reading the result in inches or centimeters. A rigid tape measure will straighten the line instead of following the spine's curve, producing an inaccurate, shorter number.
Common torso-length ranges
Size bands differ by maker, and every brand's own chart is the authority for its packs. As one published example, Granite Gear's chart runs:
Torso Length
Common Size Label
15–18 in
Short
18–21 in
Regular
21–24 in
Long
Height is not a substitute for this measurement — two hikers of the same height can have noticeably different torso lengths, since torso-to-leg ratio varies by individual, not by overall stature.
One method, with one important exception
The C7-to-iliac-crest method on this page is the norm. Gregory, Osprey, Hyperlite and ULA all define torso length from the C7 vertebra to the iliac crest,1,2,3,4 and Deuter defines back length as the distance from the seventh cervical vertebra to the upper edge of the iliac crest.5
Not every brand does it this way. Mystery Ranch measures from C7 down the spine to a point just behind the belly button,6 which gives a different number from the same body. The takeaway: measure once using the standard landmarks, but when a brand publishes its own method, follow that brand's instructions before reading its chart.
Finding the bottom landmark reliably
The hip landmark causes more errors than the neck one, because it is a line rather than a bump. Granite Gear describes it as the point where your thumbs point across your back when your hands are on your hips,7 and Gossamer Gear suggests cupping the hip bones and finding the center point on the spine between them.8 ULA describes the end point as where the iliac-crest line crosses the spine.4
Gregory's instructions say to place your hands on your hips and slide up to the top ridge of the hip bone,1 while this page says to slide down until the thumbs catch the ridge. Either direction works as long as the thumbs end on the top edge of the bone, not the soft waist above it or the side of the pelvis below it.
Reading the result against a chart
Size bands are a general pattern, not a verified standard. Real charts differ. Granite Gear offers Short (15 to 18 inches), Regular (18 to 21) and Long (21 to 24),7 while Deuter's regular fit targets a back length of about 46 cm and its EL fit about 50 cm.5
One more wrinkle: some guides describe a straight-line distance rather than a tape that follows the spine's curve. Brands mostly describe measuring down the spine, and Big Agnes says straight down the spine to the iliac-crest line.9 The difference is small, but for a borderline result it is worth measuring twice. Kelty notes that a torso measurement is only a starting point for fit,10 so try the pack on with weight before deciding.
