Bibliographic format

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Bibliographic format (also known simply as "format") refers to the proportional relationship between a full sheet of paper and the folded and cut leaves of a book. For example, a text printed two-up so that the sheet of paper needs to be folded once to make the leaves of a book is in "folio" format. A book printed four-up on a sheet that's folded in half, then in half again, is a "quarto" and so on. Bibliographic format is usually determinable on books from the hand-press era (roughly 1450 to 1830), when books were routinely printed on hand-made sheets of paper. For machine-press books, it is usually impossible to tell the actual format of the book, regardless of any printed signatures present, unless it is bound loosely enough to see the sewing in the middle of the gatherings.

Same words, different meanings

Many of the same terms were long used as standard names for paper of various sizes (often known as "Imperial standard" size), the same way we now talk about "A4 paper" or "letter size paper". Then, beginning in the 19th century, the terms started being used to indicate a book's height: "octavo" means "little", "quarto" means "ordinary size", "folio" means "big", and "elephant folio" means "huge". Many libraries, including the Folger, use these size designations to describe sections of shelving in the stacks. For example, the "folios" section is for books with a spine height of 30.1 cm through 50 cm, or oblong with a width of 23.1 cm and up (anything bigger than that would be in the "flats" section).

When someone associated with the Folger refers to "a folio," you have to rely on context to know if they mean an oversize book, a book in in folio format, or one of the first four editions of Shakespeare's collected plays. Similarly, you have to know from context whether a researcher interested in the "the same work in different formats" is interested in different bibliographic formats, different media types (play, opera, movie, etc.), different carrier types (DVD, VHS tape, etc.), or what.

Bibliographic format in Hamnet records

Hamnet records for vault material display the bibliographic format in parentheses at the end of the "Description" field, after the book's height (rounded up to the nearest centimeter) when applicable. You can keyword search this portion of the description on Hamnet's "Advanced Search" tab by choosing "Size/Format" from the "Search in" menu. Hamnet records use the "DCRM(B)" abbreviations found in the left-hand column of the chart in this article. Hamnet screen showing size and bibliographic format.png

Abbreviations and names for formats

This chart lists abbreviations and names for each of the main bibliographic formats. The column on the far left shows the abbreviations used in Hamnet.

DCRM(B)[1] Gaskell[2] Ordinary spoken English Latinate spoken English Other
full-sheet 1⁰ broadsheet, full sheet
fol. 2⁰ folio folio fo., 1/2⁰, f⁰, F
4to 4⁰ quarto quarto 1/4⁰, Q⁰, Q
8vo 8⁰ octavo octavo 1/8⁰, O
12mo 12⁰ twelvemo duodecimo 1/12⁰, D
long 12mo long 12⁰ long twelvmo long duodecimo
16mo 16⁰ sixteenmo sextodecimo 1/16⁰, S
18mo 18⁰ eighteenmo octodecimo 1/18⁰
24mo 24⁰ twenty-fourmo vicesimo-quarto 1/24⁰, T
long 24mo long 24⁰ long twenty-fourmo long vicesimo-quarto
32mo 32⁰ thirty-twomo trigesimo-secundo 1/32⁰, Tt
48mo 48⁰ forty-eightmo quadragesimo-octavo Fe
64mo 64⁰ sixty-fourmo sexagesimo-quarto 1/64⁰, Sf
72mo 72⁰ seventy-twomo
96mo 96⁰ ninety-sixmo
128mo 128⁰ one-twenty-eightmo

NB. for search-and-replace updating to DCRM(B) abbreviations:

  • character following the number may be:
    • degree symbol
    • superscript zero
    • superscript lower-case letter "o"
  • be careful of the order of operations, e.g. change "12⁰" to "12mo" before changing" 2⁰" to"fol." or you'll end up with "1fol."


  1. Descriptive Cataloging of Rare Materials (Books), the international standard for rare books in library catalogs.
  2. Philip Gaskell, A New Introduction to Bibliography. Reprinted with corrections in 1995. New Castle, Del.: Oak Knoll Press, 2007