Packing a backpack so it carries

Two people can carry the same 14 kg and have entirely different days, and the difference is usually where the dense items sit. Weight held away from your back works on a lever: the further the mass is from your spine, the harder it tries to rotate you backwards, and the more you lean forward to cancel it. You hold that lean all day, and your lower back pays for it.

So the first rule is distance from your back, not height in the pack. Dense, heavy things go hard against the back panel; light, bulky things fill the space out towards the lid. A 2 kg food bag pressed to the frame and the same bag in the outer half of the pack are not the same 2 kg.

Height is the second rule, and where the folklore goes wrong. Heavy-at-the-bottom advice comes from external-frame packs and from unstable ground. With an internal frame and a hip belt — 75 of the 80 packs in this catalogue have a frame — the heavy items belong level with your shoulder blades and tight to your back. Low down, the load hangs behind and below you, so the pack sags and the straps pull on your shoulders instead of pressing the frame into your hips.

Treat the main compartment as three bands: a bottom zone under your lower back, a core against the back panel level with your shoulder blades, and a top zone plus the lid. Each has a job, decided by density and by when you next need the item.

The pad is the awkward one. A rolled foam mat travels strapped outside or lining the inside wall; an inflatable one packs to between 1.8 l and 6 l here — the 8 and 9 litre entries in the pool are all rolled foam — and is best slid down the side of the core, where it stiffens the load. On the 5 frameless packs in the pool it is the only structure there is.

Do the volume arithmetic once. Median tent 7 l, median bag 6.5 l, median pad 3.5 l: 17 l of a median 58 l pack gone before food or clothing. Across the full spans those three run from about 7 l to 46 l, which is why capacity advice means nothing until you know what you own. What size backpack you need works that through.

1. 1

   Empty it and lay everything out

   On the floor, in one layer. You cannot pack in the right order out of a pile, and this is when you notice the two head torches and the tent bag with no pegs in it.

2. 2

   Put the liner in first

   If you are using one, and the last section argues that you should, it goes in before anything else and opened out into the corners. A liner shoved in halfway through the job is how kit ends up outside it.

3. 3

   Sleeping bag into the bottom, loose

   Not in its stuff sack if you can help it. Stuffed straight into the base of the liner it flows into the corners and wastes no space. Push it down and out to the sides, not in as a brick.

4. 4

   Build the dense core against the back panel

   Food, stove, fuel and water stacked vertically against the frame, heaviest item level with your shoulder blades. Water is the densest thing most people carry at 1 kg per litre, so it sets the tone.

5. 5

   Fill every void around the core

   Tent and clothing pack into the outer half and down the sides, wedging the core so it cannot migrate. Voids are what let a load shift. Poles and pegs go down one side, vertically, never across the top.

6. 6

   Load the top and the lid for the weather

   Waterproof, warm layer, headtorch, first aid and day food go in last. The test is whether you can get a waterproof on in sideways rain without opening the main compartment.

7. 7

   Compress, then shake it

   Pull the side and lid straps in, bottom upwards, then lift the pack by the haul loop and shake it hard. Anything you hear move is a void you did not fill, and it will thud against your back for the next four hours.

The moment you need a waterproof is the moment you least want to open a pack. Rain arrives with wind, at the least sheltered point of the day. Pack for that moment specifically.

• Waterproof jacket, and overtrousers if the forecast has earned them. Lid or top of the pack, never the bottom.
• A warm layer for stops, plus hat and gloves from autumn to spring: almost no weight, and the fastest change in body temperature available to you.
• A headtorch, always, even on a day walk. The trip you finish in the dark is the one you did not plan to.
• Map, phone, snacks and water in the hip belt and side pockets. First aid and a repair kit in the lid, where somebody else can find them — looking after your kit covers what belongs in that kit.

A frame can only transfer a load that is held still. Under-fill a pack and the contents sit in a lump that slides away from the back panel and swings with each step. That swing is work, and the lever arm you spent the first section minimising opens up again every time the load moves outwards.

So a 70 l pack carrying 35 l of kit is worse than a 45 l pack carrying the same kit. Compression straps get some of it back, but they squeeze the pack into an hourglass rather than flattening it against your back, and past a point they stop helping. Capacities here run 27 l to 80 l with a median of 58 l: buy near your usual trip, not your longest one.

A well-packed pack can still be worn badly, and the usual mistake is fastening the shoulder straps first. Your shoulders are not load-bearing the way your hips are. The hip belt goes on first and carries the weight; every other strap exists to stop the pack moving.

1. Loosen everything before you lift it — shoulder straps, load lifters, hip belt. A pack put on tight cannot be seated properly.
2. Lift it onto a raised knee, a wall or a rock, then swing one arm through and shrug it across.
3. Stand up straight, settle the hip belt padding over the top of your hip bones, and pull it firm. Firm, not crushing: you should be able to breathe out fully and still feel it carrying.
4. Now snug the shoulder straps until they follow the shape of your shoulders. They hold the pack against you; they do not hold it up. If the weight has moved onto them, the belt is too low or too loose.
5. Pull the load lifters until they run at roughly 45 degrees and the top of the pack comes in against you. Snug only: cranking them lifts the load off your hips. Then fasten the sternum strap loosely, level with your armpits.
6. Walk ten minutes, then retighten the hip belt. The load settles, and so do you.

If the belt will not hold the weight however you adjust it, the pack is probably the wrong length for your back rather than worn out. Packs are sized by torso length, not height, and the pool here covers 38 cm to 58 cm. That is why the finder asks for a back measurement rather than how tall you are.

No backpack sold for walking is waterproof. The fabric may be coated, but the seams are sewn, the zips are not sealed and the lid is a flap. Weather resistant means the contents stay dry in a shower and get wet in a day of rain. Plan for that, because a soaked down sleeping bag does not insulate at all, and a night in the hills in a bag that does not insulate is a safety problem rather than a discomfort.

If you carry one, carry the liner: a roll-top dry bag, or a heavy-duty rubble sack, which costs almost nothing and works. Carry both and the pack is dry inside and not much heavier outside. Inside the liner, give the sleeping bag its own dry bag along with one set of sleep clothing that never comes out for any reason except sleeping. That set is what makes a soaking day recoverable.

Down and synthetic fail very differently when this goes wrong, and if you walk somewhere reliably wet the fill type matters more than the rating. Down or synthetic has the argument in full.