The Perfect Fit:
How to Buy the Right Size Hiking Backpack
When choosing your hiking backpack you'll notice that most packs are available in different sizes. Usually, those sizes are small, medium, and large.
Step 1: Measure Your Torso Length
The easiest way to do this is to ask a friend for help. Simply measure the vertical distance from your neck (the bony bump at the base of your neck) to your the center of your back at the hip bones. Get a SMALL hiking backpack if the length is 16" or smaller, get a MEDIUM hiking backpack if your torso length is 16.5" to 19.5", and get a LARGE hiking backpack if it's 20" and up.
Step 2: Measure Your Hip Size
The size of your hips is less important than torso length but is still worth checking. To measure it, take a tape and measure around your hips (from your belly button to your sides and to your hip bones). Most hiking backpacks can accommodate a wide range of hip sizes, but here's a tip: Adjust the belt size so that it straddles your hips about an inch above and below the line we just measured. It should wrap around your two (pointy) pelvic bones in front. That's the perfect position for optimal comfort and weight relief.