A4 paper[paper?:paper sample maker cutting machine] is the standard paper size used worldwide, with the exception of countries in North America. The United States (U.S.), Canada, and Mexico have standardized on 8.5 inch by 11 inch (about 21.5 cm by 28 cm) paper. A4 paper is slightly longer, at 8.3 inches by 11.7 inches (about 21 cm by 29.7 cm).
A4 and the other A paper sizes are based on metric measurements. An A0 piece of paper, when spread flat, equals one square meter. A0 paper, folded in half, is a size A1. A1 folded in half is A2, and so on through A6.This produces paper with different sizes, but all with a 1.414:1 height-width ratio.
