A0 is a square meter. Its sides are self similar, such that the ratio of long to short edge stays the same when you cut one in the middle, and thus create a new long and short edge.
Each cut produces two sheets of the next Ax number, so A4 is four times halved compared to A0, or a sixteenth of a square meter.
That property of being able to halve is achieved with a ratio of the square root of 2, so unfortunately the measurements in absolute numbers get pretty odd.
Add in the fact that paper manufacturers round the numbers down, that “perfect” half size goes out the window immediately on the first division. And gets worse as the paper size gets smaller.
Since A series sizes share the same aspect ratio, they can be scaled to other A series sizes without being distorted, and two sheets can be reduced to fit on exactly one sheet without any cutoff or margins.
Why does A4 have an odd number of millimeters? Why not 290, flat?
A0 is a square meter. Its sides are self similar, such that the ratio of long to short edge stays the same when you cut one in the middle, and thus create a new long and short edge.
Each cut produces two sheets of the next Ax number, so A4 is four times halved compared to A0, or a sixteenth of a square meter.
That property of being able to halve is achieved with a ratio of the square root of 2, so unfortunately the measurements in absolute numbers get pretty odd.
Add in the fact that paper manufacturers round the numbers down, that “perfect” half size goes out the window immediately on the first division. And gets worse as the paper size gets smaller.
Definitions and math:
The answer is actually fairly interesting
https://en.wikipedia.org/wiki/Paper_size#A_series
Here is an awesome video about it: The >A paper scale, and how it doesn’t exactly subdivide
You’ll like B series paper then