It’s happened to all of us.

You start your trip with a  perfectly packed suitcase, and when it is time to go home  and cram your clothes in there, all the exact same stuff seems  to have magically expanded. It is always harder to get the  bag closed on the return trip.

And that’s because physics is working against you. As it always seems to be,  especially during physics class. So, naturally, physicists have  studied this to figure out the ideal way to fold your clothes  and absolutely stuff that carry-on.

They didn’t actually  specifically research carry-ons. But we can apply their  findings to packing clothes. And we’ve squeezed it all into this video on how science says you should pack a suitcase. [♪ INTRO] In the masterpiece that is a well-packed suitcase, each folded t-shirt acts like a single LEGO brick.

They all fit together because of their shape. But there is, of course, variety among LEGOs. And just like a LEGO’s shape  determines where you can put it, the way you fold a particular piece of clothing determines where it fits in your bag.

And we can use math to figure out what the ideal clothing “brick” looks like. Starting with a thing called the volume fraction. That’s the volume of your shirt divided by the space it occupies after folding or crumpling.

And that number gives you an idea  of how condensed the shirt is. For example, a flat piece of  paper doesn’t take up much space, just the volume of its fibers.  Its volume fraction is 1. And that’s what you want  when packing your suitcase.

But if you crumpled up that same piece of paper, it would take up much more space without having any additional material, so its  volume fraction is much less than 1. And that’s not ideal. So on a scale from 0, you’re wasting  a lot of space in your bag, to 1, you’ve perfectly solved the packing puzzle, here’s how different packing  techniques measure up.

Starting with the “It’ll Definitely Fit” crumpler. The strategy here is to throw your clothes in the suitcase and smush with all your might. Sure, this saves you time.

But I’m sorry to break it to you:  you’re paying that second bag fee. See, if you crumple your shirt into a ball, it takes up a deceptively large amount of space. We know this from experiments  on crumpled aluminum sheets.

The outer section of the crumpled  ball might pack in relatively well, forming flat-ish layers that  stack up on top of each other. And based on all the wrinkles  you’ll find upon unpacking, you might assume this method is pretty efficient at condensing the shirt into a small volume. But an X-ray view of the  crumpled ball reveals that the inside part is 30% less dense, and there’s no stackable order to the chaos in there.

Several experiments have  shown that crumpled sheets, even those compressed with very strong forces, only have a volume fraction of about one-quarter. So even if you got your strongest  friend to smush your suitcase, you’re leaving three-quarters of the space empty. Which explains why your clothes don’t fit as well on the way back if you're packing them this way because you just gotta get out of the hotel.

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But we’re only making a limited number, so get them while you can  at Complexly.store/calendar or the link in the description. Much to the chagrin of laundry-haters everywhere, wrinkles take up a shocking amount of space. All that air between fabric folds really adds up.

So it might be worth it to take  notes from the next person… The “Neat As a Pin” folder. This person precisely folds each piece of clothing into the same dimensions, ensuring  identical packing “bricks”. As boring as it is, neatly folding your clothes does significantly increase your volume fraction.

This is because the layers  of clothes are mostly flat on top of each other, eliminating  the low-density spaces that plague the crumpling method. In theory, by folding carefully, your volume fraction could be very close to 1. But!

Of course clothes can’t  be folded perfectly flat. There will always be bends that  leave empty space along the crease. So in practice, the volume  fraction is a little less than one.

And the more times you fold something, the more empty space you introduce. This is especially true for  very thick or stiff materials, so if you’re packing bulky sweaters or jeans, you’re better off folding those just once. Finally we have the “I Saw  This on CleanTok” roller.

This person carefully rolls  their clothes into cylinders. These cylinders have similar volume  fractions to neat folding, but with the added benefit of a convenient  shape if you’re packing a duffel bag or any other container that doesn’t  have perfect 90 degree corners. When you’re filling a  rectangle, you want the stuff you’re putting inside to also be rectangles so you don’t lose a bunch of space in the corners.

But if your bag has flexible  sides or odd corners of any kind, the math officially recommends you roll as many of your clothes as possible. The cylindrical “bricks” can line curved surfaces, or fit into those weird crevices  made by the suitcase handle. But it matters how tight you roll the cylinders!

If you have super strength and  roll your shirts really tightly, you’ll end up with cylinders  that are hard to deform. Since its cross-section is a circle,  you’re basically left packing circles into a box, which is a  surprisingly difficult thing to optimize. In a 2D assessment of circles  crammed into a square, the very best case scenario ends up covering  about three-quarters of the space.

Which, applied to packing, leaves one-quarter of your bag totally empty. Luckily, your shirts probably squishier  than just circles in geometry. Alternatively, you can roll your shirts into less rigid cylinders  by leaving a little slack.

This allows them to squish together until your bag’s cross-section looks more like a honeycomb. In fact, bees build hexagonal honeycombs precisely because of their optimal packing properties. If the cylinders are squishy enough, you can get a volume fraction of 9/10ths.

Meaning that CleanTok has  successfully lifehacked once again. So physics has spoken: depending  on what you’re packing and what you’re putting it in, your best strategy  is either neatly folding or rolling. See?

You never know when you’ll need to fold a little physics into your everyday life. [♪ OUTRO]