Sheet sizes?

The largest standard size, A0, has an area of 1 m². The long side of the sheet is calculated by taking the 4th root of 2, approximately 1.189, and the short side is the inverse of that number, approximately 0.841, and multiplying by one metre. A1 is formed by cutting a piece of A0 in half, which retains the aspect ratio. This particular measurement system was chosen in order to allow folding of one standard size into another, which cannot be accomplished with traditional paper sizes.