The best backpack for you is the one that fits your body the best. One of the keys to finding that right backpack is to get one that is the correct size (e.g., small, medium, large). your see what —not your height—is the key measurement.
In order to accurately determine this key spec, you’ll need a friend and a flexible tape measure.
Tilt your head forward and feel for the bony bump where the slope of your shoulders meets your neck. This is your 7th cervical (or C7) vertebra—and the top of your torso length.
On each side of your body, slide your hands down the ribcage to the top of your hip bones (aka the iliac crest). With index fingers pointing forward and thumbs pointing backward, draw an imaginary line between your thumbs. This spot on your lumbar is the bottom of your torso measurement.
Stand up straight and have your friend measure the distance between the C7 and the imaginary line between your thumbs. That’s your torso length.
Last step is to measure your hip size, wrap your tape measure around the top of your hips, hugging the iliac crest you found when measuring your torso length. This line is slightly higher than your beltline, so hip belt size differs slightly from pant-waist size.
MENS
Fits Torso Length (in.)
S: 17-19 inches
M: 18-20 inches
L: 19-21 inches
Fits Waist/Hips
S: 32-40 inches
M: 34-42 inches
L: 34-46 inches
WOMENS
Fits Torso Length (in.)
XS: 15-17 inches
S: 16-18 inches
M: 17-19 inches
Fits Waist/Hips
XS: 30-38 inches
S: 32-40 inches
M: 34-44 inches
Children (one size)
Fits Torso Length (in.)
12-16 inches
Fits Waist/Hips
22-36 inches