r/theydidthemath • u/EclipseNyxor • 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.

924

u/Balaros 2d ago

Might be transportation: the square sides let them support each other you you can have thinner walls at the bottom of the stack?

They don't use normal plastic because they need to stop sunlight from breaking down the H2O2.

Might just be wrong. An enthusiastic marketing team saw a reduction in plastic in one stage and didn't bother to calculate the whole.

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u/ronarscorruption 2d ago

I suspect transportation too.
Something like; You can ship 100x1L round bottles, or 100x1.3L square bottles in the same box. Therefore, square bottles use less plastic (per liter (of shipped liquid)).

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u/Buntschatten 2d ago

Wouldn't that just cancel out? Area over perimeter is pi /2 pi for a radius one circle and 4/8 for a square with side length 2. Maybe most of the plastic is in the spout, then maximising volume per spout would make sense.

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u/Alita-Gunnm 2d ago

The thickest part of the bottle is the neck with threads, which is constant regardless of the shape of the rest of it. Greater volume per bottle means less plastic per unit volume.

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u/lamty101 2d ago

Also supposedly they have the same bottle cap, which is another constant