令是纸张的单位。一令就是五百张纸。短令是480张纸，长令(perfect ream)是516张纸。短令是20个short quires，一令是20个quires，一个长令(perfect ream 或 printer's ream)是21.5个short quires。

在印刷中使用色令为计价的单位，指500张纸印一色。如果500张纸双面各印四色就是8色令。

Various measures of paper quantity have been and are in use. Although there are no S.I. units such as quires and bales, there are ISO and DIN standards for the ream. Expressions used here include U.S. Customary units.