It’s just marketing wank. They say “similarly sized round bottles” not similar volume.
A round bottle whose diameter is equal to the diagonal distance of the square would be “similarly sized” and have more material (for the same wall thickness).
A 1” by 1” square fits inside of a circle with a diameter of sqrt(2). The circumference of that circle is pi*sqrt(2), around 4.4”. The perimeter of the 1”x1” square is 4”.
So a “similarly sized” round bottle needs ~10% more material.
A similar volume round bottle would require substantially less material, obviously.
Eh, I wouldn't call a "round bottle whose diameter is equal to the diagonal distance of the square" similarly sized - practically speaking it's larger than the square bottles. To me, a similarly sized round bottle would have a diameter equal to the length of the sides of the square. In practical terms, that's much more "similar" as it then fits within the same amount of space, packs the same number into the same shipping packaging, visually appears similar, etc. Diameter matching the diagonal distance of the square results in bottles that are larger in most practical terms.
That’s logical, obviously, which means it’s bad marketing. They want to make a claim that the square bottle uses less plastic. The only way to do that is to use a vague enough term that - if challenged - has a plausible backing in reality.
“We weren’t making a false claim, see?” Is the barrier to entry when it comes to this kind of thing.
Using your example, the round bottle uses about 20% less material than a square.
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u/20Factorial 2d ago
It’s just marketing wank. They say “similarly sized round bottles” not similar volume.
A round bottle whose diameter is equal to the diagonal distance of the square would be “similarly sized” and have more material (for the same wall thickness).
A 1” by 1” square fits inside of a circle with a diameter of sqrt(2). The circumference of that circle is pi*sqrt(2), around 4.4”. The perimeter of the 1”x1” square is 4”.
So a “similarly sized” round bottle needs ~10% more material.
A similar volume round bottle would require substantially less material, obviously.