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.

Quarto as format

A quarto (from Latin quārtō, ablative form of quārtus, fourth) is a book or pamphlet made up of one or more full sheets of paper on which eight pages of text were printed, which were then folded two times to produce four leaves. Each leaf of a quarto book thus represents one fourth the size of the original sheet. Each group of four leaves (called a "gathering" or "quire") could be sewn through the central fold to attach it to the other gatherings to form a book. Sometimes, additional leaves would be inserted within another group to form, for example, gatherings of eight leaves, which similarly would be sewn through the central fold.