Things to know when selecting a backpack1. Determine what you really want to do with the backpack.Having an idea what you are going to do with the backpack is key. This might sound obvious but if you intend to do a lot of long tough hikes you will need a different backpack compared to if you are hiking your local park for a few hours. For those long tough hikes, an ultralight hiking pack is a smart way to save your back from tough pain. However, for those short hikes, the extra cost for ultralight hiking pack might not be worth it as you probably won't be moving around with that much stuff.  2. Determine Exactly What You Want to Haul.Backpacks come in a variety of shapes and sizes. The key is finding the right size for your intended travel. A common rule of thumb for understanding the best backpack size for your next journey is the following: If you are planning a weekend trip, aim for a bag with 35-50 liters/ 2000 to 3000 cubic inches. If you are planning a week or so trip, aim for bag with 50 to 80 liters/ 3000 to 4500 cubic inches.  If you are planning a trip longer than a week, aim for a backpack with 70 liters or higher/ 4000 cubic inches.  Step 3: The Correct Fit = Torso Length:When selecting a backpack for fit, you want a bag that falls into this general rule of thumb. One measures torso length from your shoulders to the top of you hip bone. Backpack SizeTorso LengthExtra small Up to 15 inchesSmall16 to 17Medium18 to 19Large20 To Learn Even More Check Out Our Beginner's Guide to Selecting a Backpack.