Units of paper quantity was ordered by the ream of 480 sheets. In 1840, a ream in Lisbon was 17 quires and 3 sheets = 428 sheets, and a double ream was 18 quires and 2 sheets = 434 sheets; and in Bremen, blotting or packing paper was sold in reams of 300 (20 quires of 15 sheets). A mid-19th century Milanese-Italian dictionary has an example for a "risma" (ream) as being either 450 or 480 sheets. In the UK in 1914, paper was sold using the following reams: Reams of 500 sheets were mostly used only for newsprint. Since the late 20th century,
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