What size backpack do you need: litres, torso length and fit
A pack has two sizes and only one of them is printed on the front. Litres decide what fits inside. Torso length decides whether you can carry it.
Two sizes, and only one is on the label
Every pack has a capacity in litres and a frame size in centimetres of back length. The litres are in the name. The frame size is buried in a specification table, and it is the one that decides whether the pack works.
The 80 packs here run from 27 to 80 litres, with a median of 58, and between them they cover torso lengths from 38 cm to 58 cm. Those two spans are independent. A 60-litre pack exists in more than one back length, and the right litres in the wrong back length is a bag that hangs off your shoulders for four days.
Comfortable maximum loads across the pool run from 10 kg to 30 kg. That is the manufacturer estimate of how much weight the frame and belt can move onto your hips and still be pleasant, and it is the number to check against what you actually intend to carry. A pack rated for a load it cannot transfer to your hips is a pack you carry with your shoulders and your lower back. Where the pack sits in the kit as a whole is covered in how to choose a backpacking kit ; this guide is about the two numbers on the pack itself.
How many litres
Litres follow nights, but not in a straight line. The first night costs the most volume, because the shelter, the bag, the pad and the stove all go in whether you are out for one night or five. Each night after that adds food and very little else.
| Trip | Capacity | Where that sits here |
|---|---|---|
| One night, summer, compact kit | 30–40 l | The small end. The smallest pack in the pool is 27 l. |
| Two or three nights, three-season | 45–55 l | Just under the 58 l median. |
| Up to a week, or carrying a share for two | 55–70 l | Around and above the median. |
| Winter, or a week with bulky kit | 70–80 l | The top of the pool. The largest pack here is 80 l. |
The trap at the top of that range is that an over-large pack gets filled. This is not a theory. Empty space invites the third fleece and the second book, the pack gets heavier, and the litres you bought for flexibility become kilos you carry. If you are between two sizes and your kit is compact, take the smaller one. Cutting base weight is far easier in a pack with no room for the things you do not need.
The better version of this calculation uses packed volume rather than trip length. The other three items at catalogue medians are 7 litres of tent, 6.5 of bag and 3.5 of pad: 17 litres before anything else goes in. Add your food, water, clothing and stove, and buy for that. How you pack then changes how much of the remainder you can actually use, because volume you cannot reach is volume you do not have.
Measuring your torso
Torso length is the distance between two bones you can find with your fingers. Height has very little to do with it — two people of the same height can have noticeably different back lengths, which is precisely why the frame size is measured rather than inferred. Get someone to help, because you cannot hold a tape on your own neck and read it at your hip.
Find the top
Tip your head forward and run a finger down the back of your neck. The bone that stands out most where the neck meets the shoulders is the C7 vertebra. That is the top of the measurement.
Find the bottom
Put your hands on your hips with thumbs pointing backwards and fingers forwards, so the edge of each hand rests on the shelf of bone at the top of the pelvis — the iliac crest. The point on your spine level with your thumbs is the bottom of the measurement.
Measure between them
Have someone run a soft tape down the line of your spine from C7 to the thumb line, following the curve of your back rather than cutting a straight line through the air. Stand normally while they do it. That figure in centimetres is your torso length, and the packs here cover 38 cm to 58 cm of it.
Match the stated range, not the letter
Brands cut that span into different numbers of sizes and label them differently, so a medium from one maker can overlap a small from another. Ignore the letter and check the torso range the maker states for that specific pack. If you fall on the boundary between two sizes, try both loaded and keep the one that puts the hip belt on the crest with the shoulder straps still wrapping your shoulders.
Hip belts are a separate fit from back length, and waist measurement does not follow torso length. If the belt cannot be tightened onto the crest of your hips — not around your waist, which is soft and higher up — the pack is wrong for you however well the back length matches. Many packs have interchangeable belts for exactly this reason.
Where the load should sit
The point of a frame is to move weight off your shoulders and onto your pelvis, which is built to carry it and attached to your legs. The usual rule of thumb is that a well-fitted pack puts most of the load through the hip belt — commonly quoted as 70 to 80 per cent — with the shoulder straps doing little more than holding the pack against your back.
You can feel whether it is happening. Loaded and standing, your shoulders should be able to take a rest: loosen the shoulder straps a couple of centimetres and the weight should stay where it is, sitting on your hips. If loosening them drops the load onto your arms, it was never on your hips in the first place, and no amount of tightening will fix a back length that is wrong.
Internal frame or frameless
Seventy-five of the 80 packs here have an internal frame and five have none. That is not a fashion split. It is a load split.
A frameless pack has no structure to transfer weight, so there is nothing to move the load to your hips with. Everything you put in is carried by your shoulders and by your back staying upright under it. It saves real weight — the lightest pack here is 500 g against a median of 1,400 g — but it asks for things in return: a genuinely small base weight, a packing discipline in which the sleeping pad or a foam sheet becomes the frame, and kit that will not dig into your spine when it is pressed against your back.
Experienced walkers disagree about where the ceiling sits. You will see it quoted anywhere from 7 kg to 12 kg of total loaded weight, and the honest answer is that it depends on your back, your packing and how far you are walking. The decision rule is simpler than the argument: if you have never weighed your loaded pack, you are not yet a candidate for a frameless one. Weigh it with food and water in. Under about 9 kg, frameless is a real option; above it, the framed packs are where to look. The pack pool records which is which.
Testing a pack in a shop
A pack that feels fine empty tells you nothing at all. Ask the shop to load it — most will, with beanbags or rice sacks — to roughly the weight you expect to carry, then spend ten minutes on it.
- Loosen everything, then tighten in order: hip belt first, sitting on the crest of the hips rather than the waist; then the shoulder straps; then the load lifters; and the sternum strap last.
- Stand still for two minutes without talking. Discomfort that shows up in two minutes in a shop shows up in twenty on a hill, multiplied.
- Walk, and if there are stairs, use them. Climbing is where a frame that is too long catches the back of your head, and where a belt that is slightly too loose starts to slide.
- Bend forward as if picking something up, then look over each shoulder. The pack should follow your body rather than swinging after it.
- Loosen the shoulder straps by a couple of centimetres. The load should stay on your hips. If it drops, the back length is wrong or the belt is in the wrong place.
The finder cannot do this part. It asks for a height band because that is the most an honest form can ask without a tape measure in the room, so treat what it returns as a shortlist of packs worth putting on rather than as a fitting. Start there , then go and load one.
Packs already chosen for particular trips:
Questions readers ask
- Does my height decide my pack size?
- No. Packs are sized by torso length, the distance from the C7 vertebra to the top of the hip bones, and people of the same height vary in it. The packs here cover 38 cm to 58 cm of back length and each one states its own range. Measure first, then match.
- What size pack do I need for a week?
- Between 55 and 70 litres suits most people, which sits around the 58-litre median of this catalogue. Food is what grows with the nights; the shelter, bag and pad go in either way. If your kit is bulky rather than heavy, volume matters more than the number of days.
- Is it safer to buy a bigger pack?
- It is the commonest mistake in this pool. Spare volume gets filled and the weight follows it. If you are between sizes and your kit is compact, take the smaller pack and accept that a rare long trip means being disciplined rather than buying for it now.
- What does comfortable maximum load mean?
- It is the manufacturer estimate of the load the frame and belt can move onto your hips and still carry pleasantly. Across this pool it runs from 10 kg to 30 kg. It is not a structural limit: going past it usually means the pack stops carrying well long before anything breaks.
- Do women-specific packs matter?
- They are a different frame geometry rather than a different category: generally a shorter back length range, a hip belt shaped for a different pelvis angle, and narrower, more curved shoulder straps. Fit decides it, not the label. Try both if your measurement sits in the overlap.