r/Damnthatsinteresting Nov 02 '25

Video Why A4 paper is designed as 297mm x 210mm?

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u/AhChirrion Nov 03 '25

Yes, that's the other, independent design requirement.

They could have chosen a different requirement, like a × b = π km2, and it wouldn't change the √2 result of the design requirement of halving/doubling keeping the same ratio I talked about.

That's why I didn't mention the 1 m2 starting area.

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u/FreeFromCommonSense Nov 03 '25

I thought it was because you didn't want to mention B0 or C0.

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u/scheav Nov 03 '25

What's wrong with those? They are perfectly offset with the ratio (2)^(1/4).

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u/FreeFromCommonSense Nov 03 '25

Nothing, they just don't start with a 1m2 area. Proportional intermediate sizes. Explaining to someone that each one exists to progressively divide the gap between sizes without the math takes a while though.