When and why did A4 become the standard size for paper?

Question

...and did I put this in the wrong category? I couldn't really find one where it seemed to fit.

Answer 1

No one has answer the "why" part of your question, which is by far the more interesting.

The 'A' series of paper sizes has one characteristic that is not shared by other sizes, like foolscap, quarto, octavo, and so on. If you take a piece of A0, and cut it along the longer side, you get two pieces of A1, and if you take A1 and cut it along the longer side, you get two pieces of A2, and so on. But the curious thing is that for each resulting sheet, the ratio of the longer to the shorter side is always the same.  Each sheet in the series is just a smaller (or larger) version of the next.  Think about what happens when you cut a square, for example. The resulting pieces are different shapes from the original.  

Only rectangles whose longer to shorter sides are in the ratio of the square root of two have this property, that they preserve their shapes on successive cuttings or foldings. No other shape has this property. If you know a little bit about Pythagoras' theorem, you can work out why this cutting/folding property should be.

A0 size was chosen such that its area is one square metre, and the sides in the ratio SQRT(2) : 1.  A1 is half a square metre in area, A2 a quarter square metre, and so on down the series.

'C' series paper has an area slightly larger, allowing for space around the sides of 'A' series paper when used as envelopes, which is why envelopes come in Cx sizes.

Answer 2

Look at the following sites,

The Straight Dope: How did 8-1/2x11 and 8-1/2x14 become the standard ...

The Straight Dope: How did 8-1/2x11 and 8-1/2x14 become the standard paper sizes? ... Letter paper in Europe is a size called A4, which is 210x297 millimeters--about ...

www.straightdope.com/classics/a3_016.h... - Cached

Talk:Paper size - Wikipedia, the free encyclopedia

Why is the standard paper size in the U.S. 8 _ " x 11" ... Or did this books publisher use a paper size they thought was standard, and ...

en.wikipedia.org/wiki/Talk:Paper_size - 84k - Cached

Between Borders " A4 vs US Letter

And a scale representation of each page size reinforces the ... paper (and related series such as the C-series for envelopes) started to become the standard. ...

betweenborders.com/wordsmithing/a4-vs-...

Answer 3

Not the wrong category.  Just fine.  Here is wrong category:  "QU:  How many books did Samuel Clements write?" placed in the Health category of Y/A.

But to answer your question.  I do not know and here is another bit of anomaly:  the size of paper in the United States is not A4, but is called "letter size" and it is 8.5 inches by 11 inches.  See?

Difficult.  No one gave a standard at the beginning of paper making and so the machines are made for different sizes.  Like copiers and all that.