When it comes to backpack fitting, the best place to start is by taking your torso measurement. This video offers easy instruction on determining your torso size.
There’s certainly a number of factors to consider when selecting the appropriate backpack for your next outing or adventure. That can include size capacity, pack weight and your intended usage of that pack. When it comes to fit, however; the starting point really should be taking your torso measurement and making sure you’ve got a pack with the appropriate torso fit range.
Taking your torso measurement is not difficult; in fact it’s pretty easy. It’s that much easier if you employ a second set of hands. Standing upright as you would as though you just put on your backpack and are ready to take off, lower your chin towards your chest. When you do that, a vertebra will protrude from the top of the shoulders to the base of the neck; you can’t miss it. Using a flexible tape measure, (and that flexibility is important), follow the contours of the spine right down to a point that is even with top of the hip bones, or the iliac crest. Remember that it's important to measure to the top of the hipbones and not further down the leg.
The person being measured should point their thumbs inward to helps the measurer identify exactly the point to measure to at the bottom of the spine. Keep in mind that torso sizing can differ in regards to different backpack brands in the way that measurements can differ with clothing by different brands.
Men’s torso lengths with backpacks often fall between 17 and 21 inches. Women’s, on average, might be 14 inches to 18 inches, but that range can differ dramatically; we’re all different. It’s important to actually take that torso measurement before you backpack shop. Height feels like it should be a determinant, but isn’t necessarily so. You could be 6’ 6” and be all legs with a short torso, or 5’ 2” and have a longer than average torso measurement.