The size of a modern book is based on the printing area of a common flatbed press. The pages of type were arranged and clamped in a frame, so that when printed on a sheet of paper the full size of the press, the pages would be right side up and in order when the sheet was folded, and the folded edges trimmed.
The most common book sizes are:
- Quarto (4to): the sheet of paper is folded twice, forming four leaves (eight pages) approximately 11-13 inches (ca 30 cm) tall
- Octavo (8vo): the most common size for current hardcover books. The sheet is folded three times into eight leaves (16 pages) up to 9 ¾" (ca 23 cm) tall.
- DuoDecimo (12mo): a size between 8vo and 16mo, up to 7 ¾" (ca 18 cm) tall
- Sextodecimo (16mo): the sheet is folded four times, forming sixteen leaves (32 pages) up to 6 ¾" (ca 15 cm) tall
Sizes larger than quarto are:
- Folio: up to 15" (ca 38 cm) tall.
- Elephant Folio: up to 23" (ca 58 cm) tall.
- Atlas Folio: up to 25" (ca 63 cm) tall.
- Double Elephant Folio: up to 50" (ca 127 cm) tall.
Sizes smaller than 16mo are:
- 24mo: up to 5 ¾" (ca 13 cm) tall.
- 32mo: up to 5" (ca 12 cm) tall.
- 48mo: up to 4" (ca 10 cm) tall.
- 64mo: up to 3" (ca 8 cm) tall.