With the exception of the United States, Canada and some other American countries the ISO 216 standard paper sizes determine the length of the sides of sheets. These paper sizes are based on a common side scale (1: square root of 2). This standard made sense if the 1960s with the spread of photocopiers, using the scale was more effective than anything else. Using the side scaled can be useful also when resizing, for example, an A3 sheet can be enlarged without distortion to A2. The maximum standard paper size is A0. The area of this is 1 square meter. With folding in half of this size we can get A1, so the scale will remain. With folding in half of the longer side we can get the further sizes.