I think it's mostly that you get a lot more mechanical advantage when tightly rolling than stacking flat, which allows a lot more air to be squeezed out. Once rolled, it's also easier to prevent it expanding: you just have to stop it unrolling, not by applying constant pressure to the whole surface. This is easier in smaller bags like backpacks actually, as compared to big hardshell cases, as it keeps the rolls fixed in place.<p>What gets tighter: wrapping tape around something or laying it along something?
When rolling up clothes, you push some air out before you try closing your suitcase.<p>Also, I think packing the various parts into a container _feels_ a bit easier with rolled-up clothes than with folded ones (relatively flat, with slightly varying dimensions), at least partly because you’re a bit more inclined to compress them into a space.<p>The bin packing problem for rolled up clothes also may be easier than that for folded clothes, mathematically, but I can’t think of an argument as to why it would be.
I've tried the rolled-clothes method of packing many times and have yet to be able to squeeze in more clothes than simply laying them flat or folded.
I'm also very curious to know if someone has any scientifical evidence that rolling is more efficient than normal flat stacking.
And that it is not just cargo cult trend following Marie Kondo popularity.<p>I have this argument with my gf each time we are packing.<p>From my point of view, for tshirts, in a standard luggage, when they are stacked flat, I can put more of them as they can easily be squeezed vertically.
If you have 12" wide objects to stick into a 23" wide suitcase, you can't stick two of them side by side, so you have 11" of dead space because you're an inch short on making them divide evenly.<p>If you can roll it into a 3" wide tube to fit into the same suitcase, even though you're still an inch short of fitting an extra object into the case, you only have 2" of dead space.
I find the big advantage of rolling to be easier access to the rolled items at my destination. I can pick a rolled shirt or pants to wear without rooting through a stack of folded clothes, which usually results in some of the stacked items getting wrinkled.
A game changer in this regard is packing cubes or compression cubes.<p>Usually rectangular not cube shaped but they come with a double layer of zips, one set to get inside the cube and another set that once the cube is full you can zip up all the way around and it will squash everything down. I fly 4-6 trips (8-12 flights) a year and never travel without them.
I think part of it is they squish or can fit to shape differently than folded, meaning they can become sorta a hexagon sort of shape once compressed against eachother, and that’s the most efficient space filling shape.
Also, like others said you don’t have to keep pressure on it to keep its state.