Why suitcase cubes fight a backpack
Open a clamshell travel pack and you have a rectangle roughly 21 x 14 x 9 inches. A large suitcase cube is often 17 or 18 inches on its long edge, which means it fits one way round and only one way round. Once it is in, everything else has to work around it, and the corners it cannot reach are dead space — typically a liter or two you paid for and cannot use.
In a top-loading pack the problem is worse, because you are stacking rather than laying out. A tall stack of two mediums is stable and searchable; a single large cube wedged sideways means unloading the bag to reach anything under it.
The practical rule: in a 35–40L pack, medium and small are the only sizes that earn their place. Buy a set for the mediums and smalls and leave the large ones at home. That is true of every set on this page, including the six- and eight-piece ones — the extra pieces are spares and options, not a packing plan.
How many cubes to carry
Four, assigned by category rather than by size:
- Tops— shirts and t-shirts, folded or rolled, in a medium.
- Bottoms and layers— trousers, a mid-layer, in a second medium.
- Small items— underwear, socks, a swimsuit, in a small.
- Laundry— a compression cube, which shrinks as it fills with things that no longer need to look good.
That fourth one is the trick that makes cubes genuinely worth carrying in a backpack. Dirty clothes are the ideal compression candidate: you do not care if they wrinkle, and compressing them buys back the volume the clean clothes are steadily vacating. Run it that way and your bag stays roughly the same fullness all trip instead of overflowing by day four.
More on the system in how to use packing cubes, and the prior question — whether to carry any at all — in are packing cubes worth it.
The weight, which nobody prints
A set of cubes is not free. Fabric, zips and pulls add up to a real figure, and on a carrier that caps cabin bags at 7 kg it comes out of your clothing allowance before you pack a single item. Almost no cube maker publishes a per-piece weight, which is why our spec tables read “Not published” on that row rather than guessing at one.
What you can control is the count. Four cubes instead of eight is the single largest saving available in this category, and it costs you nothing you will miss. The airline-by-airline cabin weight table is in carry-on weight limits by airline.
Compression cubes in a backpack
Compression cubes have a second zip that squeezes air out after the cube is full. In a backpack they are more useful than in a suitcase, for a specific structural reason: a pack has no rigid shell to hold shape, so a compressed cube actually makes the whole bag smaller rather than just leaving a gap inside a hard case. On a soft 40L bag facing a strict sizer, that is the difference between a bag that clears and one that bulges.
The trade is wrinkles, and it is real. Compress knitwear, fleece, laundry and anything you will not be photographed in; do not compress a shirt you need to look pressed. The full comparison, including true compression bags, is in packing cubes vs compression bags.
What to look for in a cube for a pack
- Mesh tops or a window. In a bag you cannot lay open on a bed, seeing the contents without unzipping is worth more than in a suitcase.
- A grab handle on the short edge. This is how you extract a cube from a deep pack without unloading the ones above it.
- Soft, unstructured sides.Stiffened cubes hold a rectangle you have to accommodate. Soft ones deform into the pack’s curves, which is what you want in a bag with no flat walls.
- Zips that run past the corners. A zip that stops short means you are posting clothes through a slot rather than opening a lid.
- Water resistance if you swim. A damp swimsuit in a coated cube is a one-cube problem. In an uncoated one it is a bag-wide one.
The honest case against
Cubes buy order, not space. In a backpack they cost you a little volume and a little weight, and they give you back the ability to find a t-shirt on day nine without excavating. For most people that trade is easily worth it; for a genuinely ultralight traveler carrying five days of clothing in a 26L pack, four cubes are four cubes too many and a single stuff sack does the job. Buy the number that matches the bag, not the number that comes in the box.
