Paper size
From Craft-Wiki
Almost all countries in the world use ISO 216 A4 as their standard paper size, which measures 210 by 297 millimeters (8.27 in × 11.7 in).
A few countries use the Letter (ANSI A) size (or US Letter), which measures 8.5 by 11 inches (215.9 by 279.4 mm).
Each of these two paper sizes can be cut and folded in a specific way to create standard card bases.
