Packing a Backpack: Heavy Close and Centered, Light on Top, and the Things You Need Outside

In four zones from the bottom up. Bottom: the sleeping bag and anything else soft and bulky you will not need until camp. Core: the heaviest things, water, food, stove, fuel, pot, batteries, packed against the back panel between your shoulder blades. Around and above the core: the tent body and clothing layers, stuffed to fill gaps so the heavy items cannot shift. Top and lid: the rain shell, an insulating layer, lunch, anything light you may want in the next hour. Pockets and hip belt: the things you reach for all day. Then cinch every compression strap so the load is one solid block.

Against the back panel, centered left to right, at the height of your shoulder blades: water, food, the stove and fuel, the pot, a big battery. That puts the weight over your hips, where the belt carries it, and keeps the pack's center of gravity close to your own so it does not lever you backward on climbs or swing on traverses. On rough ground and scrambles some people drop the heavy core a few inches for a lower center of gravity; on trail, shoulder-blade height is right.

Heavy close to the spine and centered, bulk below and above it, light on top, and balanced side to side: a full water bottle in each side pocket, not one. Fill every gap with soft things so nothing moves; a load that shifts is a load that throws you. Use the compression straps to pull the whole pack tight against your back. Then put it on, adjust the hip belt and load lifters, and walk fifty yards; if it pulls back or sways, the heavy things are too far from your spine or too high.

Everything you will want without stopping and unpacking: water bottles or the hose, snacks and lunch, sunscreen and lip balm, the map and compass or the phone with maps, a headlamp, the water filter, the first aid kit, the rain shell when weather is close, the knife, toilet paper and a trowel, bug spray, and a hat and gloves. Hip belt pockets for snacks, phone and sunscreen; the lid for the first aid kit, headlamp and map; side pockets for water and the shell; the front stretch pocket for wet or bulky things.

Because the weight is too far from your spine: heavy items packed against the outer face of the pack, or high in the lid, or the whole load riding loose. Every inch the weight sits away from your back multiplies its pull. Repack with the heavy things against the back panel between the shoulder blades, fill the gaps so nothing shifts, tighten the compression straps, and snug the load lifter straps at the top of the shoulder straps until the top of the pack sits close to your head instead of leaning away.

Loosen every strap, put the pack on, and settle the hip belt so its padding wraps the top of your hip bones with the center of the belt over the crest, then buckle and cinch it tight; that is the step everyone skips. Then tighten the shoulder straps until they wrap the shoulder without lifting the belt off the hips. Then the load lifters, the small straps from the top of the shoulder straps to the pack, pulled until the pack tips in to about 45 degrees. Then the sternum strap, snug but not tight. About 70 to 80 percent of the weight should be on your hips. If the belt sits on your waist or your shoulders ache in an hour, the torso length is wrong for you, which is an adjustment on most packs and a different pack on some.

For a fit adult on a trail, around 20 percent of body weight carries well and 25 percent is a hard day: 30 to 40 pounds for most people. A go-bag you may have to carry far when you are tired, hurt or with children should be lighter, 10 to 15 percent, because the day you carry it is the day you are not at your best. Kids carry 10 percent at most. Water is the heaviest thing in any pack at 2.2 pounds a liter, which is why a filter and a map of water sources cut more weight than any gear upgrade.