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Why are beverage cans usually round? Considering the amount that are made, and the need to be transported - isn't a round design inefficient? (ie the lost space from not tightly fitting together).

Is there a usability impact on a round can vs a squared can for one handed drinking use?

enter image description here

There is a related question here but I believe the physical properties of aluminium mean there is a difference here.

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    Well, they're easier to hold, for one thing.
    – Vitaly Mijiritsky
    Commented Mar 15, 2016 at 17:10
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    In addition to weak points at the corners, a square can would need significantly thicker walls to prevent them bulging out due to the pressure contained by the can. Even an uncarbonated beverage would probably cause noticeable bulging in a square can over a period of time.
    – brhans
    Commented Mar 15, 2016 at 18:57
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    Did you do any research on this before posting this question?
    – JonW ♦
    Commented Mar 16, 2016 at 10:27
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    You say these cans are usually and typically round, but I've never seen non-round cans in my life. Could anyone link some images?
    – user1306322
    Commented Mar 16, 2016 at 14:57
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    Is this really a UX question? Seems more of an engineering question. Kind of like the ones discussed here: What's the deal with “what's the deal with X” questions?
    – sumelic
    Commented Mar 16, 2016 at 20:36

3 Answers 3

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It is a combination of manufacturing and usability... but mostly manufacturing.

Doing a quick web search for "why are soda cans round" (Google does a decent job) yields multiple insights in the issue. But the only result you need to visit is engineerguy's YouTube video (you should also be Subscribed to engineerguy, because he is awesome).

The Ingenious Design of the Aluminum Beverage Can

enter image description here

The answer of why a soda can is shaped the way it is is answered in the first 1 minute and 40 seconds.

3 options are explored:

Sphere:

Pro:

  • Uses the least amount of material
  • No corners, so no weak points when under pressure

Cons:

  • Difficult to manufacture
  • Rolls off the table (a usability point)
  • When packed together, only 74% of volume is taken up by product

Cuboid:

Pro:

  • Sits on the table
  • Easier to manufacture

Cons:

  • Awkward to drink from (a usability point)
  • Edges are weak points, requiring thick walls

Cylinder:

Pro:

  • Elements of both shapes
  • 91% of packing space used by product
  • Round shapes can maintain itself under the pressure of its contents (both inward and outward pressure)
  • Can be easily held (there's the usability answer)
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    The density of optimal packing isn't really relevant if it's not used. I'm not familar with cans, but bottles are usually packed in a square formation, not in a hexagonal formation, reducing the density to 78% (pi/4).
    – CodesInChaos
    Commented Mar 15, 2016 at 19:56
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    That video was awesome. Now I want to know why beans don't come in nitrogen-pressured beverage cans.
    – Chris Chudzicki
    Commented Mar 15, 2016 at 20:48
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    @CodesInChaos cans are often packed in hexagonal arrangement. See, e.g.: pacepalletservices.com.au/wp-content/uploads/2012/12/…
    – Jules
    Commented Mar 15, 2016 at 21:53
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    @CodesInChaos Perhaps it has something to do with once the cans are placed inside a box? If the cans were in a hexagonal formation and then inside consumer boxes (like a 12-pack) it seems like there would be more appreciable spaces between the inset cans and the box wall - creating weak/crush spots if stacked inappropriately.
    – Ramrod
    Commented Mar 15, 2016 at 22:25
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    Most cases of soda pop cans in stores I've seen (USA/Canada) are packed in a "square" formation, similar to bottles but with no cardboard separators. Even big flats of 36 (like at Costco) are square packed, though they usually end up a little squished & kind of "hexagonal" packed, just from picking them up by the sides only, kind of like this image ezorder.com.sa/Images/Products/OM9103.jpg.
    – Xen2050
    Commented Mar 16, 2016 at 2:10
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Other people have already said "manufacturing" so I will not repeat that.

What is worth emphasizing though is that soda cans are pressurized to 2 atmospheres of pressure or more.

https://www.youtube.com/watch?v=EJiUWBiM8HE

Side-note: this is why the container is made of metal in the first place. Few other packaging materials can deal with this load while maintaining any kind of integrity or stability, the other competitors chiefly being glass or PET.

The cylinder deals with this easily since the load becomes equal in all directions, and it is simple to strengthen it at the top and bottom. The cylinder maintains its shape under pressure.

A square shape on the other hand will start deforming. Pressure on a flat surface will cause it to bulge. Just as it is impossible to pull a hanging wire until it is straight without sagging, you cannot subject a flat surface to pressure without bulging.

For non-pressurized products, other package shapes are common, the square one as well. But for pressurized products, you will find that cylinder packaging is next to universal.

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    This is the true answer - applying pressure to a non-round container tends to make it into a round one.
    – pjc50
    Commented Mar 16, 2016 at 12:01
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    @pjc50 Ahh... I understand now! So they actually do make the "cans" box-shaped. The reason they look cylindrical to us is that they have completed their transformation. (Every one, uniformly perfect)
    – TOOGAM
    Commented Mar 17, 2016 at 4:31
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Update: I should have done more research on the topic. Thanks for @fractalspawn's clarification.

Actual manufacturing process of the modern soda can is pressing and extruding it. https://www.youtube.com/watch?v=V7Y0zAzoggY

I think it's more due to the manufacturing process. A round can is easier to produce by curving the sheet around a drum. It stores more volume of liquid per amount of metal used. Aluminum is more expensive than the rectangular cardboard packaging for the flats. Makes way more sense to optimize for aluminum cost to have round cans than to optimize it for "storage".

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    I could be wrong, but I think they way they make a can is to actually take a disc of aluminum and put it in a press and extrude it. They then apply the lid and roll it closed creating the lip. This is why the only seam on the can is where the lid meets the body.
    – coblr
    Commented Mar 15, 2016 at 19:04
  • @fractalspawn I'm pretty sure I've seen the same thing on one of those "How It's Made" or "Factory Made", etc. programs.
    – Monty Harder
    Commented Mar 15, 2016 at 19:53
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    -1 because drinks cans aren't made the way described in this answer (source: Alcoa).
    – David Richerby
    Commented Mar 15, 2016 at 20:32
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    @novice: I thought "turning" was something done with a lathe. Seems like a waste for a cheap can. Looking at sources for aluminum can prod, they use the term "drawing".
    – coblr
    Commented Mar 16, 2016 at 18:19
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    The term of art for the technique is spinning, and items made using it are said to be spun. Aluminum is particularly easy to spin because it's rather ductile. And yes, it's done on a sort of lathe, but not by removing material with a cutting tool. Drawing is what you to with wire.
    – Stan Rogers
    Commented Mar 20, 2016 at 21:25

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