In book publishing we’ve become used to using the word “format” to mean a range of things from the layout of a page of type, to the trim size of the book, or even sometimes just to the type of binding, hardback or paperback. Among the public nowadays the layout meaning has elbowed its way to the top of the heap, as we all busily format our documents on our computers. In common parlance the word has become almost a synonym for arrangement in the sense of mise en scène. The primary definition, according to The Oxford English Dictionary, is however “the shape and size of a book, e.g. octavo, quarto, etc.” The word is just lifted from the French and ultimately Latin.

In his ABC for Book Collectors John Carter says about the original basic usage of the term “format”: “In bibliographical contexts it is used to indicate the structure of a volume in terms of the number of times the original printed sheet has been folded to form its constituent leaves . . . Thus in a folio each sheet has been folded once, in a quarto twice, in an octavo three times; the size being thus respectively a half, a quarter and an eighth that of the original sheet.”

He provides a handy list of nomenclature, with the abbreviations you may meet. Note that the naming system starts from leaves, not pages*:

  • Folio (Fo., sometimes 2o). Folded once — two leaves; four pages.
  • Quarto (Qto, 4to, 4o). Folded twice — four leaves; eight pages.
  • Octavo (Oct., 8vo, 8o). Folded thrice — eight leaves; 16 pages.
  • Duodecimo (12mo, 12o).
  • Sextodecimo (16mo.) Folded four times — 16 leaves; 32 pages.
  • Vicesimo-quarto (24mo)
  • Tricesimo-secundo (32mo). Folded five times — 32 leaves; 64 pages.

In order to get to the real size of a book in inches or centimeters these names need to be associated with a sheet size, for example Crown quarto, Royal octavo, Demy octavo (Demy is pronounced like deny/defy, and indicates a sheet measuring 22½” by 17½”. If you insist on doing the mathematics, remember to leave a trim allowance!). Other sheet sizes may be found at that Demy octavo link. When I started out in book manufacturing these ancient names of sheet sizes were dropping out of common usage: most had years earlier, but Crown and Demy would still be heard. The longest surviving is Demy octavo, which in Britain designates a pretty standard book size, 5½” x 8½” as we describe it in America. It just means a Demy sheet folded three times, to yield a sixteen-page section. Nowadays of course paper is bought and sold not with these antique designations but by inch/centimeter dimensions. The conservatism in nomenclature is justified by the fact that presses would have been constructed to accommodate efficiently certain sizes of paper: if you thought of your press as a Crown press, you might be inclined to refer to its product in the same terms. Plus of course we all love to impress visitors with our fluent and expert use of obscure jargon.

Be it confessed that though I have arranged printing in 64-page sigs for lots of books (mostly bibles, because that many pages in a section demands a thin paper) I have never heard anyone utter the words “thirtytwomo, or Tricesimo-secundo. (A “g” instead of that “c” is what I’d have expected: a variant apparently.) I wonder if there’s anyone alive today who’s ever spoken either word, or indeed the two above in that list. Maybe an antiquarian bookseller or two?

See also Duodecimo.


* Well, strictly speaking, it’s actually based on proportions of the sheet. For example a quarto section lying there in front of you will show you a quarter of the original sheet surface, which of course means four leaves, eight pages.