The A4 format ( often called A4) is the world's most common and one of the standardized in DIN 476 and ISO 216 formats for writing papers. It is 210 mm wide and 297 mm high. Its name refers to the fact that it A0 arises after four central folds of the reference format ( 841 mm x 1189 mm = 1 m2).
The standardized series of paper sizes ( rows A, B, C and D) have an aspect ratio of ( about 1 to 1.41 ), the arising of this election, the central folds on the two small leaves on it.
When four-time folding the reference format A0 (area equal to 1 square meter), the area is reduced to one-sixteenth. Thus an A4 sheet weighs 5 grams at typical grammage of 80 g / m² (80 grams per square meter).
The predominant use of A4 size are adjusted most briefcases and loose-leaf binders and most printers and copiers.
DIN 476 was created in 1922, which was resorted to a draft at the time of the French Revolution. Later it was the international standard ISO 216, which is followed in almost all countries of the world (except USA and Canada).