Units of paper quantity Units of paper quantity 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. A quire of paper is a measure of paper quantity. The usual meaning is 25 sheets of the same size and quality: of a ream of 500 sheets. Quires of 25 sheets are often used for machine-made paper, while quires of 24 sheets are often used for handmade or specialised paper of 480-sheet reams. (As an old UK
Paper size any size can be made by using sheets of the next larger size, e.g. A4 sheets are folded to make A5 brochures. The system allows scaling without compromising the aspect ratio from one size to another—as provided by office photocopiers, e.g. enlarging A4 to A3 or reducing A3 to A4. Similarly, two sheets of A4 can be scaled down and fit exactly on 1 sheet without any cutoff or margins. The behavior of the aspect ratio is easily proven: on a sheet of paper, let "a" be the long side and "b" be the short side; thus, = . When