A Guide to Antiquarian Book Sizes: Understanding Terms for Collectors

For collectors of antiquarian books, the variety of sizes and formats can seem daunting, especially when terms like folio, quarto, and octavo appear in catalogs or listings. These terms, rooted in early printing practices, describe the physical format of a book based on how many times a sheet of paper was folded to create its leaves. Unlike modern books, which are often described by precise measurements in inches or centimeters, antiquarian book sizes use a specialized vocabulary that reflects their historical production. This guide explains the traditional book size terms, their approximate dimensions, and the types of books collectors might encounter, helping you navigate the world of rare and historical books with confidence. Whether you’re hunting for a grand Shakespeare folio or a compact duodecimo prayer book, understanding these formats will enhance your collecting experience.

The Origins of Antiquarian Book Sizes

In the hand-press period (up to around 1820), books were made by printing text on large sheets of paper, which were then folded, gathered into groups called signatures or gatherings, and bound. The number of folds determined the book’s format and size:

• A folio (from Latin folium, leaf) involved one fold, creating two leaves (four pages when printed on both sides).
• A quarto (from Latin quartus, fourth) required two folds, producing four leaves (eight pages).
• An octavo (from Latin octavus, eighth) involved three folds, yielding eight leaves (sixteen pages).

These terms originally referred to the format—the folding process—rather than precise dimensions, as paper sizes varied across time, region, and printer. For example, a folio printed on a royal sheet (25 x 20 inches) would be larger than one printed on a demy sheet (22.5 x 17.5 inches). Over time, bibliographers and booksellers assigned approximate height ranges to these terms for clarity, though collectors should note that actual sizes depend on the original sheet and trimming during binding. Today, many booksellers provide measurements (e.g., 12 x 9 inches) alongside traditional terms to avoid confusion.

Why Book Size Matters for Collectors

Antiquarian book sizes are more than technical jargon; they offer insights into a book’s production, purpose, and historical context:

• Rarity and Value: Larger formats like folios were expensive to produce, often reserved for prestigious works (e.g., Shakespeare’s folios), making them highly collectible.
• Purpose and Audience: Smaller formats like duodecimos were portable and affordable, suited for personal use, such as prayer books or pocket editions.
• Aesthetic and Condition: Size affects a book’s proportions (folios are upright, quartos squarish, octavos smaller and upright), influencing shelf appeal and preservation needs.
• Bibliographic Significance: Format reveals printing techniques, such as the number of leaves per gathering or the imposition (arrangement of pages on a sheet), aiding authentication.

For collectors, understanding these terms helps decipher listings, assess a book’s authenticity, and appreciate its place in printing history. A folio in 8s (a folio with gatherings of eight leaves) is distinct from a standard folio, for example, and such nuances can affect value.

Common Antiquarian Book Size Terms and Formats

Below is a detailed guide to the primary antiquarian book formats, their approximate sizes, abbreviations, and the types of books collectors might encounter. Sizes are based on typical heights in inches, reflecting trimmed leaves, though variations occur due to paper size, trimming, and binding. All measurements are approximate and assume a standard sheet (e.g., 19 x 25 inches in the U.S. or similar in Europe).

1. Folio (Fo., 2°)

• Definition: One fold, producing two leaves (four pages) per sheet.
• Approximate Size: Over 13 inches tall (33 cm), often 12 x 19 inches (305 x 483 mm) or larger, up to 50 inches for double elephant folios.
• Characteristics: Large, upright-shaped books, often on high-quality paper (e.g., royal or imperial stock). Folios were costly, used for prestigious or reference works.
• Common Types:
• Literary masterpieces (e.g., Shakespeare’s Fourth Folio, 1685, ~14.5 x 9.25 inches).
• Religious texts (e.g., Bibles, liturgical books).
• Scientific or historical works (e.g., atlases, natural history volumes).
• Large-format art or architecture books (e.g., elephant folios, 23–25 inches, or atlas folios, 25–50 inches).
• Examples:
• Shakespeare’s Fourth Folio (1685), a large folio with an engraved portrait, printed on royal stock, valued for its stateliness and rarity.
• Audubon’s Birds of America (double elephant folio, ~40 x 27 inches), a monumental work requiring custom binding.
• Collector Notes: Folios are prized for their grandeur but require careful storage due to size and weight. Check for first state imprints or untrimmed margins, which increase value. Variants like folios in 8s (multiple leaves inserted for binding) are common.

1. Quarto (4to, 4°)

• Definition: Two folds, producing four leaves (eight pages) per sheet.
• Approximate Size: 10–13 inches tall (25.4–33 cm), typically 9.5 x 12 inches (241 x 305 mm), squarish in proportion.
• Characteristics: Medium-large, squarish books, balancing cost and readability. Quartos were versatile, used for a wide range of texts.
• Common Types:
• Early plays and poetry (e.g., Shakespeare’s quarto editions of individual plays).
• Scholarly works (e.g., philosophy, theology, law).
• Illustrated books (e.g., early scientific treatises with engravings).
• Examples:
• Shakespeare’s Romeo and Juliet (1597, first quarto), ~7.5 x 5.5 inches, a rare survivor of early play printing.
• Galileo’s Dialogue Concerning the Two Chief World Systems (1632), often in quarto for its diagrams.
• Collector Notes: Quartos are highly sought after for their historical significance, especially for early English literature. Look for chain lines and watermarks to confirm format, as modern reprints may mimic quarto size. Squarish proportions distinguish them from folios and octavos.

1. Octavo (8vo, 8°)

• Definition: Three folds, producing eight leaves (sixteen pages) per sheet.
• Approximate Size: 8–10 inches tall (20.3–25.4 cm), typically 6 x 9 inches (152 x 229 mm), upright-shaped.
• Characteristics: Small to medium, upright books, the most common format for early modern books due to affordability and portability. Variations include crown octavo (5.38 x 8 inches), royal octavo (6.5 x 10 inches), and imperial octavo (8.25 x 11.5 inches).
• Common Types:
• Novels and literature (e.g., 18th-century fiction, poetry).
• Religious texts (e.g., Books of Hours, sermons).
• Scientific or medical texts (e.g., early anatomy books).
• Examples:
• Samuel Johnson’s A Dictionary of the English Language (1755), often in octavo for accessibility.
• Jonathan Swift’s Gulliver’s Travels (1726), typically an octavo for broad readership.
• Collector Notes: Octavos dominate antiquarian collections due to their prevalence. Check for octavo in 4s (four-leaf gatherings) or untrimmed edges, which add value. Variants like royal or imperial octavo are larger and more luxurious.

1. Duodecimo (12mo, 12°)

• Definition: Folded to produce twelve leaves (twenty-four pages) per sheet, often with complex folding patterns.
• Approximate Size: 7–8 inches tall (17.8–20.3 cm), typically 5 x 7.375 inches (127 x 187 mm), upright-shaped.
• Characteristics: Compact and portable, duodecimos were popular for personal use, offering a balance of readability and economy.
• Common Types:
• Pocket-sized literature (e.g., novels, essays, poetry).
• Devotional books (e.g., prayer books, psalters).
• Travel guides or almanacs.
• Examples:
• John Bunyan’s The Pilgrim’s Progress (1678), often in duodecimo for wide distribution.
• 18th-century chapbooks, cheap duodecimo pamphlets for popular stories.
• Collector Notes: Duodecimos are charming for their portability but may have small fonts, affecting readability. Look for original bindings or uncut pages, as these are often rebound. Large duodecimo (5.5 x 7.5 inches) is slightly larger.

1. Sextodecimo (16mo, 16°)

• Definition: Folded to produce sixteen leaves (thirty-two pages) per sheet.
• Approximate Size: 6–7 inches tall (15.2–17.8 cm), typically 4 x 6.75 inches (102 x 171 mm), upright-shaped.
• Characteristics: Very small and portable, used for texts meant for frequent carrying or discreet use.
• Common Types:
• Miniature prayer books or devotionals.
• Poetry collections or short stories.
• Pocket dictionaries or guides.
• Examples:
• Elizabethan poetry anthologies, like Tottel’s Miscellany (1557), often in sextodecimo.
• Early 17th-century almanacs, compact for daily use.
• Collector Notes: Sextodecimos are delicate and prone to wear, making well-preserved copies rare. Their small size appeals to collectors of miniatures, but font size can be challenging.

1. Smaller and Larger Formats

• Smaller Formats:
• Octodecimo (18mo): ~4 x 6.5 inches (102 x 165 mm), 18 leaves per sheet, used for tiny devotionals or novelties.
• Trigesimo-secundo (32mo): ~3.5 x 5.5 inches (89 x 140 mm), 32 leaves, for pocket guides or miniatures.
• Quadragesimo-octavo (48mo): ~2.5 x 4 inches (63.5 x 102 mm), 48 leaves, rare and collectible.
• Sexagesimo-quarto (64mo): ~2 x 3 inches (51 x 76 mm), 64 leaves, true miniatures, often novelty items.
• Larger Formats:
• Elephant Folio: 23–25 inches (58.4–63.5 cm), for grand illustrated works (e.g., natural history).
• Atlas Folio: 25–50 inches (63.5–127 cm), for maps or oversized art.
• Double Elephant Folio: Up to 50 inches (127 cm), for monumental works like Audubon’s prints.
• Collector Notes: Miniatures (64mo and smaller) are niche and highly collectible but fragile. Oversized folios require special storage and are often incomplete due to wear or disassembly.

Key Terms and Abbreviations

• Fo., 2°: Folio, largest standard format.
• 4to, 4°: Quarto, squarish, medium-large.
• 8vo, 8°: Octavo, upright, common for novels.
• 12mo, 12°: Duodecimo, pronounced “twelvemo,” compact.
• 16mo, 16°: Sextodecimo, pronounced “sixteenmo,” very small.
• Leaf: A single sheet of paper, with two pages (front and back).
• Gathering/Signature: A group of folded leaves sewn together for binding.
• Imposition: The arrangement of pages on a sheet for correct printing order.
• Chain Lines/Watermarks: Marks in handmade paper, used to confirm format.

Where Collectors Encounter These Books

• Rare Book Auctions: Folios and quartos dominate high-value sales (e.g., Sotheby’s, Christie’s), especially for Shakespeare, incunabula (pre-1501 books), or early scientific works.
• Antiquarian Bookshops: Offer a range of formats, with octavos and duodecimos most common. Shops like Heritage Book Shop list detailed formats (e.g., “large folio, 14.5 x 9.25 inches”).
• Online Marketplaces: Platforms like AbeBooks or Biblio list formats and measurements. Always verify descriptions for accuracy (e.g., “8vo” should match ~6 x 9 inches).
• Libraries and Archives: House folios and quartos for research, often untrimmed or in original bindings, providing context for collectors.
• Book Fairs: Events like the New York Antiquarian Book Fair showcase all formats, with dealers explaining terms like folio in 8s or royal octavo.

Practical Tips for Collectors

• Learn the Terms: Familiarize yourself with folio, quarto, octavo, etc., and their abbreviations (4to, 8vo). Use resources like the Antiquarian Booksellers’ Association size table for reference.
• Check Measurements: Since paper sizes varied, confirm listed dimensions (e.g., “12 x 9 inches”) against format terms. A “quarto” taller than 13 inches may be mislabeled.
• Examine Format Clues:
• Look for chain lines (horizontal or vertical marks from papermaking) and watermarks to verify folding patterns.
• Count leaves per gathering to confirm format (e.g., eight leaves for octavo).
• Note imposition errors (e.g., misnumbered pages), which add character and authenticity.
• Assess Condition: Larger formats (folios) are prone to wear, while smaller ones (16mo, 64mo) may have tight margins or rebinding. Untrimmed or uncut edges are valuable.
• Understand Value:
• Folios and quartos are often rarer and more expensive due to limited print runs (e.g., a Shakespeare folio can fetch millions).
• Octavos and duodecimos are more affordable but valuable if early or in original bindings.
• Miniatures (64mo) or oversized folios (atlas, double elephant) are niche and costly.
• Verify Editions: A folio may have multiple states (e.g., Shakespeare’s Fourth Folio first state lacks Chiswell’s imprint). Consult bibliographies like Pforzheimer or Blayney for details.
• Handle with Care: Use book cradles for folios, avoid opening spines fully, and store in climate-controlled conditions to prevent paper degradation.
• Seek Expert Advice: Consult dealers or bibliographers for complex formats (e.g., octavo in 4s) or to authenticate rare items.

Quick Reference Chart

Conclusion

Antiquarian book sizes, from the stately folio to the tiny sexagesimo-quarto, offer a window into the craftsmanship of early printing. Terms like quarto and octavo reflect how sheets were folded to create books, shaping their size, purpose, and audience. For collectors, mastering these terms unlocks the ability to navigate catalogs, assess rarity, and appreciate a book’s historical context. Whether you’re drawn to the grandeur of a Shakespeare folio, the squarish charm of a quarto play, or the portability of a duodecimo prayer book, understanding formats enhances your collecting journey. Next time you encounter a listing for a “4to” or “8vo,” you’ll know exactly what to expect—and how it fits into the rich tapestry of book history. Happy collecting!