16mo

16mo, or sixteenmo, is a historical book size designation used from the early modern period through the 19th century. The term denotes a format produced by folding a full sheet into sixteen leaves (32 pages). It is part of the family of “mo” formats, alongside duodecimo (12mo) and eighteenmo (18mo); the exact size varied by era and region, but 16mo generally refers to a compact, portable edition smaller than typical 12mo formats.

Physical characteristics and production methods varied, but most 16mo volumes were designed to be easily carried or stored. Typical heights ranged roughly from about 10 to 18 centimeters (approximately 4 to 7 inches), with widths depending on margins, type, and binding. They were produced by standard printing and binding processes of the time, using paper or parchment covers and similar binding to other small formats.

Historical usage and content varied, but 16mo editions were popular for affordable and portable works such as primers, sermons, tracts, travel guides, poetry, and copies of classic literature. The format offered a cost advantage over larger formats and was widely used across Europe and North America from the 16th through the 19th centuries. As printing practices evolved and standardized sizes became dominant, the 16mo format waned in common production.

In modern libraries and bibliographies, 16mo remains a descriptive designation for historical editions. It is often used to indicate the physical characteristics of older books rather than a contemporary production standard.