A Size Paper

• The length divided by the width is 1.4142.
• The A0 size has an area of 1 sqm.

Letter Size

• Defined by American National Standards Institute, letter size is commonly used in the United States, Canada, Chile, Colombia, Costa Rica, Mexico, Panama, the Dominican Republic and the Philippines.  It measures 8.5 by 11 inches (215.9 by 279.4 mm)

B Size Paper

• The length-to-width ratio is 1:root2.
• The B series paper sizes were created in order to provide paper sizes that weren’t covered by the A series.