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.