Choosing a pack to fit your body type is generally a function of two simple measurements, your torso length and your hip size. Your torso length, not your height, determines your pack size.
Your torso length doesn't actually have anything to do with your height so make sure you measure. We always prioritize the torso measurement over the height. One of the biggest mistakes new backpackers make is choosing a backpack without measuring their torso length first.
HOW TO MEASURE MY TORSO LENGTH
To find your torso length grab a soft tape measure and a friend to help out. If you don't have a soft tape measure just use the length of rope and then lay it out to measure when you're done.
Start out by tilting your head forward and finding the bony bulge at the base of your neck. That's your C7 vertebra and the top of your torso length, next find the tops of your hip bones and place your hands of your hips with your thumbs pointing towards your spine. Where your thumbs would meet in the middle of your back is the bottom of your torso length. Knowing your correct torso length will make buying the right size pack much easier.
HOW TO MEASURE MY HIPBELT SIZE
The next important measurement is your hipbelt size. Read more if you want a comfortable hipbelt with plenty of room for you to be able to cinch it down tight and loosen it up when you need to. You might lose a little weight on longer trips so make sure you have a couple of extra centimeters to be able to cinch down your hip strap tight. Your hip strap is going to be the most important load-bearing structure on your pack, so make sure it's comfortable and make sure you get this measurement right.
Most companies will allow you to choose your torso length and your hipbelt size separately for your pack and some even have removable hipbelts.
To find your hipbelt size simply take your tape measure and wrap it around your waist at the top of your hips. That's your hipbelt measurements and also the center point of where you're going to want your pack rest on your hips.
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