What makes “A” paper special?

If the rectangles are to be similar

then the ratio of sides has to be equal so

Solving for a gives

So the sides of “A” paper are in the ratio 1 : √2 linking it to one of the most fascinating and intriguing concepts in mathematics, the irrational number.

A simple check to see if paper is “A” size

Fold across one corner. Is the fold (the hypotenuse of the triangle) formed equal to the side of the rectangle. Check with another rectangle. They should be exactly equal if the paper sides are in the ratio 1 : √2

The commercial development of “A” or metric paper took place in Germany during the thirties. It had the great advantage of reducing the enormous wastage of paper in the industry as large sheets were folded to make smaller books. Now it is standard in almost every part of the world (except America!).

It also fitted into the drive to relate everything to the metric system with A1 paper having an area of 1 square metre and B1 paper having one side of the paper 1 metre long.