Universities in the U.S. increasingly use A4 size paper in laserprinters and library copying machines, because most conferencesoutside North America require papers to be submitted in A4 format andmany journals and conference proceedings are printed in A4 format.
Product information for inkjet and laser paper in the A3 and A4 paper sizes is available from the cross-reference charts (indexed by paper size):
Notice how the area of A4 paper is approximately 1/16 of a square meter (62,500 mm2), or just under that amount. This is no coincidence. Take the number 4 in "A4" paper and that is the power, or exponent to the fraction 1/2. So (1/2)4, or 1/16, as measured in square meters, is the "definition" of how much paper there should be there.