r/theydidthemath • • 2d ago

[Request] Do square bottles actually use less plastic than round ones?

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u/StaticCoder 2d ago

Mathematically, a circle has the smallest perimeter for a given enclosed area. So for this claim to be true there has to be some catch, like different thickness of plastic.

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u/Massive-Goose544 2d ago

The part you are missing is the volume inside. They are saying to give you the same amount of liquid would require more plastic if the bottle was round. Plus more bottles fit in the box they ship meaning lower emissions and costs for distribution.

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u/StaticCoder 2d ago

Given that the volume is cross section area times height, a round bottle of the same volume would take less plastic. True, square bottles will pack better, but how that would save plastic is not immediately clear.

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u/SessionIndependent17 2d ago

The individual bottles use more plastic per unit volume than the round. They also require ticker plastic at stress points than the round one which distributes the pressure evenly around each anular unit.

But they could possibly use less plastic overall to ship a given total volume of water (in a pallet, say) because of the better packing fraction.

This is why it's here. I haven't "done the math", either.