The size of a book is generally measured by the height against the width of a leaf, or sometimes the height and width of its cover. A series of terms is commonly used by libraries and publishers for the general sizes of modern books, ranging from folio (the largest), to quarto (smaller) and octavo (still smaller). Historically, these terms referred to the format of the book, a technical term used by printers and bibliographers to indicate the size of a leaf in terms of the size of the original sheet. For example, a quarto (from Latin quartō, ablative form of quartus, fourth) historically was a book printed on sheets of paper folded in half twice, with the first fold at right angles to the second, to produce 4 leaves (or 8 pages), each leaf one fourth the size of the original sheet printed – note that a leaf refers to the single piece of paper, whereas a page is one side of a leaf. Because the actual format of many modern books cannot be determined from examination of the books, bibliographers may not use these terms in scholarly descriptions.
>>>PUT SHARE BUTTONS HERE<<<
Book sizes in the context of Quarto
Quarto (abbreviated Qto, 4to or 4º) is the format of a book or pamphlet produced from full sheets printed with eight pages of text, four to a side, then folded twice to produce four leaves. The leaves are then trimmed along the folds to produce eight book pages. Each printed page presents as one-fourth size of the full sheet.
The earliest known European printed book is a quarto, the Sibyllenbuch, believed to have been printed by Johannes Gutenberg in 1452–53, before the Gutenberg Bible, surviving only as a fragment. Quarto is also used as a general description of size of books that are about 12 inches (30 cm) tall, and as such does not necessarily indicate the actual printing format of the books, which may even be unknown, as is the case for many modern books. These terms are discussed in greater detail in book sizes.