An Explanation of Book Sizes and Terms

We in the rare book trade do love our jargon. It's a fault, we know, in the same manner of any other trade though, our descriptive language has evolved to cater for some pretty specialised circumstances. One of the first giant clouds of obfuscation the outsider encounters is the way in which we evaluate the sizes of books. Basically it's to do with how many times a piece of paper of a certain size is folded and trimmed, and the eventual dimensions that gives you...

There's a somewhat frivolous, but visually descriptive explanation here, in which a member of our audience interacts with actual books.

For a more technical list, please see below (with some dimensions from Collin's "Author's and Printer's Dictionary."):

Here are some basic (and not so basic) book sizes. A few of these can be seen on nearly every rare book listing on the internet...with varying degrees of clarity and transparency. Some of the sizes below haven't been used for a good long while and some of them have me scratching my head as to their relevance.

Better explanations than my own can be found here, here, and here (that last is a complete glossary of terms from the crew at Between The Covers Rare Books, who do very good work). In addition The Antiquarian Booksellers Association website has a neat little table of relative sizes and names here.

 

 

64mo, 3½" x 2¼ " [8.9cm x 5.7cm]
Trigesimo-secundo, 32mo 4½" x 3" [11.4cm x 7.6cm]
Vigesimo-quarto, 24mo, 5" x 3½"  [12.7cm x 8.8cm]
Vigesimo, 20mo, 5" x 3" [12.7cm x 7.6cm]
Sexto-decimo, 16mo, 6to, 9" x 7½" [22.8cm x 19cm]
Duo-decimo, 12mo, 7½" x 4½" [19cm x 11.4cm]

Crown 8vo 7½" x 5" [19cm x 12.7cm]
Crown 4to 10"x7½"  [25.4cm x 19cm]
Demy 8vo 8¾" x 5½" [22.2cm x 13.9cm]
Demy 4to 11" x 8¾"   [27.9cm x 22.2cm]
Foolscap 8vo 6¾" x 4¼ " [17.1cm x 10.7cm]
Foolscap 4to 8½" x 6¾" [21.5cm x 17.1cm]
Imperial 8vo 11" x 7½"  [27.9cm x 19cm]
Imperial 4to 15" x 11  [38cm x 27.9cm]
Medium 8vo 9½" x 6  [24cm x 15cm]
Medium 4to 12" x 9½"  [30cm x 24cm]
Post 8vo 8" x 5" [20cm x 12cm]
Post 4to 10" x 8" [25.4cm x 20cm]
Pott 8vo 6¼ " x4  [15.8cm x 10cm]
Pott 4to 8" x 6¼ " [20cm x 10cm]
Royal 8vo 10" x 6¼ " [25.4cm x 15.8cm]
Royal 4to 12½" x 10  [31.7cm x 25.4cm]
Super Royal 8vo 10¼ " x 6¾" [26cm x 17cm]
Super Royal 4to 13½" x 10¼ " [34cm x 26cm]

FOLIOS
Atlas 26" x 17" [66cm x 43cm]
Crown or post 15" x 10" [38cm x 25.4cm]
Demy 17½" 11¼ " [44.4cm x 28.5cm]
Elephant 23" x 14" [58.4cm x 35.5cm]
Foolscap 13½" x 8½" [34cm x 21.5cm]
Imperial 22" x 15" [55.8cm x 38cm]
Medium 18" x 11½" [45.7cm x 29cm]
Royal 20" x 12½"  [50.8cm x 31.7cm]

PRINTING PAPER SIZES:
crown 20" x 15"
demy 22½" x 17½"
double crown 30" x 20"
double demy 35" x 22½"
doule foolscap 27" x 17"
double post 31½" x 19½"
double royal 40" x 25"
imperial 30 x 22"
medium 23½" x 18½"
post 19¼ " x 15½"
royal 25" x 20"
super-royal 27½" x 20½"

WRITING PAPER SIZES:
antiquarian 53" x 31"
atlas 34" x 26"
columbier 34½" x 23½"
copy or draft 20" x 16"
demy 20" x 15½"
double elephant 40" x 26¾"
elephant 28" x 23"
emperor 72" x 48"
foolscap 17" x 13½"
imperial 30" x 22"
medium 22" x 17½"
post, large 21" x 16½"
post, small 19" x 15¼ "
pott 15" x 12½"
royal 24" x 19"
super-royal 27" x 19"

FOOLSCAP
folio 13½" x 8½"
octavo 6¾" x 4¼ "
quarto 8"½" x 6¾"