What Is a Quarto (4to)? Book Sizes Explained
Quarto (abbreviated 4to or 4°) is a book format in which each printed sheet has been folded twice to produce four leaves (eight pages). The resulting book is roughly 9.5–12 inches tall, depending on the original sheet size. But to understand quarto, you need to understand the system of book sizes based on how paper sheets are folded — a system that has been used since the invention of printing.
The Folding System
A single printed sheet of paper can be folded different numbers of times to produce different numbers of leaves (and therefore different book sizes):
| Format | Abbreviation | Folds | Leaves per Sheet | Pages per Sheet | Approximate Height |
|---|---|---|---|---|---|
| Folio | 2° or fol. | 1 | 2 | 4 | 12–15” |
| Quarto | 4° or 4to | 2 | 4 | 8 | 9.5–12” |
| Octavo | 8° or 8vo | 3 | 8 | 16 | 7.5–10” |
| Duodecimo | 12° or 12mo | Various | 12 | 24 | 6.5–7.5” |
| Sextodecimo | 16° or 16mo | 4 | 16 | 32 | 5.5–6.5” |
Each additional fold halves the page size and doubles the number of leaves per sheet.
How It Works
Imagine a large sheet of paper fresh from the paper mill:
Folio: Fold it once. You get two leaves (four pages). The book is tall — roughly the width of the original sheet.
Quarto: Fold it twice (once in each direction). You get four leaves (eight pages). The book is half the height of a folio and roughly square in proportions.
Octavo: Fold it three times. You get eight leaves (sixteen pages). The book is the most common format for novels and general nonfiction — a standard “book-sized” book.
Each folded sheet becomes a gathering or signature (sometimes called a “quire”), which is then sewn together with other gatherings to form the textblock.
Why It Matters
Bibliographic Description
The format is a fundamental part of how bibliographers describe books. “8vo” in a catalogue description tells you immediately that the book is a standard-sized volume. “Folio” tells you it is a large, tall book. “4to” places it between.
Identification
Format can help identify editions. If a known first edition is a quarto and you are examining an octavo, it is not the first edition.
Historical Context
In the hand-press period (roughly 1450–1800), the format determined the economics of printing. A folio used fewer sheets of paper per page (but the paper cost more because of the larger sheet size), while an octavo maximised the number of pages per sheet. Publishers chose formats based on the intended audience and price point:
- Folio: Prestige publications — Bibles, law books, atlases, reference works
- Quarto: Important literary and intellectual works, plays (Shakespeare’s quartos)
- Octavo: The standard trade format for most books from the eighteenth century onward
- Duodecimo and smaller: Inexpensive pocket editions
Shakespeare’s Quartos and Folios
The most famous use of these terms is in Shakespearean bibliography. Shakespeare’s plays were first published individually in quarto format (the “quartos”) and then collected in the First Folio of 1623. The terms “quarto” and “folio” are central to Shakespeare bibliography and textual criticism.
Modern Usage
In modern publishing, books are described by their height in inches or centimetres rather than by format, because mechanised printing no longer follows the traditional sheet-folding system. A modern book described as “8vo” in a bookseller’s catalogue is being described by its height (roughly 8–10 inches) rather than by how it was literally produced.
The traditional terms remain standard in antiquarian bookselling and bibliography:
- “Crown 8vo” — a specific octavo size based on the Crown paper sheet
- “Royal 4to” — a quarto from Royal-sized paper (larger than standard)
- “Small 4to” — at the smaller end of the quarto range
For practical purposes, if you encounter these terms in a catalogue: folio means big, quarto means large, octavo means standard, and anything smaller is a pocket book.
Quick Reference for Collectors
When you encounter these format abbreviations in bookseller catalogues and auction descriptions:
| Abbreviation | Meaning | Approximate Height | Common Uses |
|---|---|---|---|
| fol. or 2° | Folio | 12–15” | Atlases, Bibles, Shakespeare First Folio |
| 4to or 4° | Quarto | 9.5–12” | Art books, illustrated works, Shakespeare quartos |
| 8vo or 8° | Octavo | 7.5–10” | Standard novels, most modern trade editions |
| 12mo or 12° | Duodecimo | 6.5–7.5” | Pocket editions, older novels |
| 16mo or 16° | Sextodecimo | 5.5–6.5” | Mass-market paperbacks, prayer books |
Most modern first editions — the bread and butter of contemporary book collecting — are octavos. When a bookseller’s catalogue lists a book as “8vo” without further comment, they are confirming it is a standard-sized volume, which is what you expect for a novel or non-fiction trade edition.
Frequently Asked Questions
Why do booksellers use Latin terms for book sizes? Convention and precision. The Latin terms refer to the number of folds in a sheet of paper, which determines both the page size and the structure of the gatherings. Modern centimeter-based measurements are used alongside these terms for clarity, but the traditional nomenclature persists because it conveys structural information that dimensions alone cannot.