Book formats explained: folio, quarto, octavo, or how to read a fold

The format of an old book tells you how the printed sheet was folded: 2 leaves for a folio, 4 for a quarto, 8 for an octavo, 12 for a duodecimo. Height does not tell you. Booksellers have used height as a shortcut since the 19th century, and the shortcut is wrong often enough to be worth understanding.

Dear bibliophiles, good day.

By Barthélemy d’Arcole, Inspector of Bibliophilic Aesthetics and Modern Heresies to the Guild of Bibliopolices (a learned society of French invention, whose members are all the same person).

In a bookseller’s description you sometimes read “small 12mo” or “tall 8vo”. The “small” and the “tall” are there to correct the format, which proves that the format is not a size. The buyer is asked to make the adjustment himself.

The format records how the printer folded the sheet that came off his press. Folded once, it gives 2 leaves, that is 4 pages: a folio. Folded a second time, it gives 4 leaves and 8 pages: a quarto. Folded a third time, 8 leaves and 16 pages: an octavo. The duodecimo, or 12mo, has 12 leaves and so 24 pages. A sheet left unfolded is a broadside (the French say in-plano). You will see the same formats written fol., 4to, 8vo, or 2°, 4°, 8°. It is one system with several spellings.

Diagram of a printing sheet, unfolded, then folded once (folio), twice (quarto) and three times (octavo)
One printing sheet and its folds. Diagram from bibliophilie.com.

The height of the finished book depends on the paper the printer started with, and paper did not come in one size. The Lyon municipal library’s Guichet du Savoir lists 18 French paper sizes, from the smallest, the pot, to the largest, the grand-monde, running from 31 × 40 cm to 90 × 120 cm. Two octavos can therefore stand at different heights.

The Folger Shakespeare Library says the same thing from the other side. Its reference page notes that the format names once designated standard paper sizes, and that in the 19th century they came to describe book height, with octavo meaning “little”, quarto “ordinary size”, folio “big” and elephant folio “huge”. That is the shortcut, and Anglo-American catalogues use it loosely. French booksellers, who have a stricter table, set their own thresholds on the height of the bound volume. Here is the French table, given as a reference and not as a rule for English-language catalogues.

FormatLeaves per sheetPagesHeight of bound volume (French trade)Typical contents
Large folio24over 40 cmBibles, atlases, show books
Folio (2°)24under 40 cmLearned works, theology, law
Quarto (4°)48under 30 cmScholarship, illustrated books
Octavo (8°)816under 25 cmOrdinary literature
Duodecimo (12mo)1224under 20 cmNovels, devotional books (18th century)
Sextodecimo (16mo)1632under 16 cmSmall classics
18mounder 14 cmCharpentier editions (19th century)
32mo3264under 10 cmAlmanacs, very small books

To use it, stand the book upright and measure the spine from the top of the board to the bottom. These figures are ceilings: a bound volume of 27 cm is a quarto, because it is over 25 cm and under 30. It is a clue and not a proof. The binder’s plough may have trimmed the margins, and sheet sizes varied. To be sure, look at the fold itself.

You can do that without taking the book apart. Look at the foot of the first page of each gathering. The printer put a letter or a number there, the signature, so that the binder could keep the gatherings in order. Often only the first half of the gathering carries one. Count the leaves up to the next signature. A gathering always has an even number of leaves, and it is wise to count two gatherings in a row, because they do not all look alike. Count in the body of the text, never in the endpapers or the preliminary pages, which mislead.

That number, together with the direction of the paper’s lines, gives the format. Hold a leaf against the light: laid paper shows lines, called chain lines. They run vertically in a folio and in an octavo, and horizontally, as a rule, in a quarto. This is the method described by the Enssib, France’s school for librarians.

Below the octavo, the Ancien Régime had its small formats: the 12mo, the 16mo and the 24mo. The 12mo is folded in two ways, giving either a single gathering of 12 leaves, the French way, or two gatherings of 8 and 4 leaves, the Dutch way. The 32mo stays rare. As for a book wider than it is tall, it is called oblong; the French say “à l’italienne”.

Beware of names. A “sextuple-octavo” and a “twentymo” do not exist. And some formats are not what their name announces: the in-18 jésus of Charpentier, in the 19th century, has the size of an old octavo, because machine-made paper came in larger sheets. The name of a format can therefore lie about the size, and sometimes about the fold.

The format also has a history. In the first decades of printing the folio dominates, and the small formats go to books of hours, devotional works and pamphlets. They existed before printing: Parisian pocket Bibles of the 13th century are known. At the turn of the 15th and 16th centuries Aldus Manutius published Greek and Latin classics in portable volumes at Venice. The 16th century kept the folio for work and study.

In the 17th century the quarto becomes the format of literature: Ronsard, Voiture and Malherbe were printed in it, living or recently dead. It is solemn without ostentation. Toward the end of the century it gives ground to the duodecimo, which the Elzevier family used for plays, in their Dutch pirated editions. Dictionaries stay in folio. Bayle’s Dictionnaire of 1697 has 2 volumes, and Diderot and d’Alembert’s Encyclopédie has 35 volumes, produced between 1751 and 1772. The Geneva edition by Pellet, in 1777-1779, republished it in quarto, with pages half the size and at a lower price. In the 18th century the duodecimo prints most literary texts, the humbler genres included. A work first issued in quarto with fine illustrations could be reissued in duodecimo in 18 volumes.

The 19th century has its heretic. In the 1840s Charpentier sold books at 3.50 francs a volume in the format called in-18 grand jésus. That is roughly the height of a modern paperback, 18 cm. Publishers were no longer bound to any format standard, and nothing ties a format name to a size.

One last precaution, for the description in front of you. When the bookseller writes “8vo?”, he hesitates, and he gives his measurement in millimetres. When he writes “small 12mo” or “tall 8vo”, it is for you to correct. In either case, do not take his word for it: count the leaves.

What is the difference between 4to and quarto?

None. Quarto is the Latin form, 4to the usual abbreviation, also written 4°. In both cases the printed sheet was folded twice and gives 4 leaves.

How do you measure the format of an old book?

You measure the height of the spine, from the top to the bottom of the board, and set it against the table. It is the booksellers’ rule of thumb, but it proves nothing: only the fold tells the format.

Why do some descriptions say “folio raisin” or “octavo jésus”?

These are names of paper, taken from the watermark the sheet carried. A jésus octavo is an octavo folded from a sheet of jésus paper. The paper name gives the starting size, which the word octavo alone does not.

Are there formats larger than the folio?

Yes: the unfolded sheet, or broadside. For very large picture books, Anglo-American libraries speak of “double elephant folio”, the largest sheet then available, about 96 × 66 cm according to Yale. Audubon’s Birds of America is the best-known case.

I measure with the ruler first, and then with the signature.

GUILDE · BdA/FORMATS

Sources: Guichet du Savoir (Bibliothèque municipale de Lyon), answers of 18/09/2023 and 14/06/2024; Enssib, “Déterminer le format” (material bibliography); BnF, glossary of the old book; Biblissima, Le livre ancien; Folgerpedia, “Bibliographic format” (Folger Shakespeare Library); Crouch Rare Books, “Book formats”; Roger Chartier, review of Isabelle Olivero, Les Trois Révolutions du livre de poche (Sorbonne Université Presses, 2022), La Vie des idées; Yale University Library on double elephant folio.

The files on the “sextuple-octavo” and the “twentymo” were closed for lack of a subject.

Document classified: restricted circulation.

La lettre du bibliophile

Si cette chronique vous a plu : recevez trois nouvelles par semaine — livres rares, reliures, enchères, et les Dossiers IGLI. 18 ans d'archives, quelques milliers de lecteurs.

Pas de pub, pas de revente de données. Désabonnement en un clic.

À lire ensuite

Hitler’s Library at the Berghof, Seized by the 2nd Armored Division (May 1945)

Dear bibliophiles, good day.

By Silas Deckard, Inspector of the Department of Altered Manuscripts (IGLI), division T – Temporality, temporal chronicler of the Guild of the Bibliopolicés.

Temporal Chronicle — infiltration report, operation Crayon Gris (“Gray Pencil”). Obersalzberg, 4–5 May 1945

I did not read what I report here in the archives. I saw it. We were set down high in the mountains, agent Raturon and I, on the morning of 4 May 1945, in the uniform of the Régiment de marche du Tchad, a unit of the French 2nd Armored Division. Serial numbers, kit and accents borrowed for the occasion. Two more men in the detachment climbing toward the nest of the man.

The mission carried a code name. The sealed order of service ran to four lines:

Infiltrate the 2nd Armored Division in its assault on the Obersalzberg. Locate and record the real state of the private library of subject A.H. No removals. No intervention. Visual record mandatory. Withdraw before 6 May.

I had accepted without argument; that is the rule. When the Guild sends an Inspector of the Temporality division, it is not to debate. One looks, one dates, one closes again.

The Guild had assigned Raturon to me — traveller of libraries, perpetually provisional secretary, entrusted for the occasion with the count.

The detachment has been climbing toward Berchtesgaden since dawn. The half-tracks stall on the hairpin bends, the engines overheat, and nobody talks about books. They talk about Munich fallen the day before, the Danube crossed, the files of prisoners in grey greatcoats coming down while we go up. Snow still clings to the slopes. One word passes from man to man, the only one that makes them lift their heads: Berghof. The subject’s house. The nest.

“The nest,” Raturon whispers beside me without taking his eyes off the ridge, “is a disappointment unaware of itself.” He already knew. On 25 April the Royal Air Force had gutted the Obersalzberg under a carpet of bombs. Then, as the Allies approached, the SS had burned what remained. We were climbing toward a carcass.

And we were not alone. Below, from the evening before, the American 7th Infantry Regiment had been the first to enter Berchtesgaden. The 2nd Armored Division pushes in the same day. The paratroopers of the 101st will arrive only the next day. Three units for one setting: the race for prestige has already begun, and History will take decades to untangle who was really first. I already know it will never quite settle the matter.

We reach the top in the fading light of 4 May. The Berghof is nothing but a smoking shell: roof stove in, blind windows, beams still warm under the ash. Men enter through the breaches, weapon in hand, out of reflex, though there is no one left to fight, only a draught and the smell of burnt wood. The tricolour soon snaps above the ruin. Two days later the American staff will firmly ask the 2nd Armored Division to come back down. Berchtesgaden will be in the American zone.

“The whole war is there,” notes Raturon, who was already filing his moral away as one classifies a statistic. “Some take the setting, others the loot. And History, out of laziness, remembers the setting.” The loot, precisely, took two forms that evening. The first flowed.

For before the books, there is wine. It is always so in war. The pantries of the Berghof, half spared, are still overflowing with spirits, cheeses, tinned food: the Americans of the 3rd Division help themselves with full haversacks before heading back down. But the real liquid treasure is higher, at the Eagle’s Nest, and it is our own men who find it: a cellar of half a million bottles. The greatest growths of France, from champagne to cognac, and whole rows of Château Lafite Rothschild — brought back from who knows what pillaging, and which French soldiers recover this evening as one recovers stolen property.

The lift at the Kehlstein has been sabotaged by the fleeing Germans. No matter: stretcher-bearers are sent up, and their stretchers — designed for bodies — come back down loaded with crates. Men pour the water out of their canteens to fill them with burgundy, throw equipment out of the tanks to fit in a few more cartons. A whole division drunk on victory and great wines.

One imagines a library as a wall of bindings, an orderly sanctuary. Think again, and let the accountant give you the figures; he was only waiting for it. “A few hundred volumes at the Berghof,” recites Raturon, stepping over the rubble of the second-floor study, now a blackened floor strewn with debris. “A crumb. Count instead the thousands of Munich, the ten thousand of Berlin. In all, nearly sixteen thousand books spread across his residences. The ground under your feet is not a library: it is an auxiliary storeroom, and it has burned.”

The real store is not here. It sleeps a few kilometres away, in a salt mine: three thousand volumes put out of the way of the bombing, which the Americans of the 21st Counter Intelligence Corps will soon carry off. “Twelve hundred will end up in Washington,” adds Raturon, who describes the future in the present tense as our condition allows. “Rare books room of the Library of Congress. And it is there, not here, that the pieces that speak are sleeping.” He lists them as a bookseller recites a catalogue: “A Schertel — Magic: History, Theory, Practice — a treatise on occultism inscribed by the author, in whose margins the subject left sixty-six strokes. A guide to Berlin by Max Osborn, dated 1909, his oldest surviving book, bought in 1915 a stone’s throw from the trenches. That is what will survive. Not the ruin: the strokes.”

Two ways of treating this loot clash before my eyes. The first is wild: a GI who has come back down to poke about pockets three volumes without even opening them. War souvenir. “Multiply by a thousand,” murmurs Raturon. “At this minute, all over Germany, hundreds of the subject’s books are slipping into haversacks. Ohio, Nebraska. Mantelpiece trinkets. Provenance lost for ever.”

The second is French, and methodical. The division’s G.5 section — civil affairs, the people who register property in occupied territory — has begun its work. Under the authority of Lieutenant-Colonel Rouvillois, every piece taken from the subject’s collections receives an ink stamp on the flyleaf: “Cette pièce provient des collections personnelles d’Adolf Hitler. Berghof. Berchtesgaden, 4 mai 1945” [This piece comes from the personal collections of Adolf Hitler. Berghof. Berchtesgaden, 4 May 1945], beneath the round seal struck with the Cross of Lorraine. More than six hundred documents will be recorded in this way; in September the division will hand over a part of them to twenty-one municipalities and to the Bibliothèque nationale, the French national library.

“Now that is serious,” approves Raturon. “In its administrative way the G.5 does what the Guild does in its own: it treats the book as an exhibit in evidence. And it is right. For these volumes are worth nothing by their text. They will be worth something through the stamp, and through what a hand did on them.” A hand, precisely. I was coming to that.

A sergeant has picked up an almost intact volume, blown under a beam, its light leather binding astonishingly spared. He hands it to me laughing — here, intellectual, you read German, don’t you — because I had been clumsy enough to decipher a sign earlier. I open it. Raturon leans over my shoulder, and I feel him freeze.

It is Fichte. The complete works of the nationalist philosopher, first edition, newly bound in white vellum. “I know this copy,” says Raturon, very low. “A gift from the filmmaker Leni Riefenstahl. The dedication reads: To my beloved Führer, with deep respect. The only real philosopher in the whole collection, in the finest binding in the whole collection — and it is a courtesan’s present to a tyrant. The centrepiece owes him nothing: it owes everything to flattery.”

I turn the pages. And I find it: a pencil underlining. A grey line, straight, drawn under a passage on the unity of the German people. Nothing else. No comment, no gloss. Just that stroke. This is what the Guild wanted me to record, I believe. Not the ruin — the ruin is spectacular, hence misleading. The stroke is tiny, and it says everything.

“Do the sum with me,” says Raturon, and it was his trade. “Out of these thousands of volumes, barely a few dozen carry an annotation in his hand. And these annotations, almost always, are not thoughts: they are underlinings. Vertical strokes. Exclamation marks. The man did not converse with his books. He sought ammunition in them. He underlined what comforted him, never what contradicted him. A reader who reads only to hear himself confirmed — the worst species, and the most widespread.”

I close the Fichte. The sergeant takes it back from me, shrugs, stuffs it in his bag. One more volume bound for nowhere.

The traveller’s thankless privilege: I know what follows. This G.5 stamp that I watch drying on the flyleaves — Berghof, 4 May 1945 — will one day become a market’s Grail. People will no longer scramble for the text, which can be found in every library in Europe; they will scramble for the stamp. Provenance as relic. A bibliophilia of horror: one does not collect the word, one collects the crime of having owned, and underlined, that word. One of the men climbing this evening — a certain Paul Gerbi, among the first to arrive up there on 4 May — will keep four albums given to the man in the 1930s, two bound in red leather, with dedications and photographs of the Führer. Decades later, a man of ninety-two, he will put them up for auction in the Vendée, in western France: knocked down for ten thousand one hundred euros. Elsewhere an entire sale will be announced under the title “Prises de guerre de la 2e DB du général Leclerc au Berghof” [War booty of General Leclerc’s 2nd Armored Division at the Berghof] — and will be withdrawn amid protests, war booty having become, with time, something that troubles.

On the morning of the 5th, as we are already being pressed to pack up, I cross an American major in the courtyard of the Platterhof. He has just arrived with the paratroopers of the 101st; behind him his men head for Göring’s cellar and its ten thousand bottles. He is in no hurry. Clean features, exact calm, the eye of a man who counts his losses rather than his loot. His name is Winters.

— You came up for the cellar, too? he asks me in approximate French, pointing at the crates being evacuated.

— For the books, I say. What is left of them.

He looks for a moment at the blackened shell of the Berghof, then barely shrugs.

— My men have earned the right to drink. Me, I only wanted to see the place. (A pause.) It is smaller than one thinks.

— Everything is, major. Especially great men seen up close.

He sketched what, in so sober a man, had to pass for a smile, and he went into the ruin without taking anything. I noted the date: his paratroopers will long tell that they were the first — they were not — and yet will sign the most famous images of the whole affair, those hilarious GIs emptying Göring’s growths at the Eagle’s Nest. That is what History will retain of the summit: not a pencil under a sentence, but happy soldiers raising bottles. And History, here again, will not be wrong. It will only have chosen the loot that can be drunk.

As for the cold record, it is another American officer who draws it up, that night, in an outbuilding of the Platterhof: a classified report on the collection. I read its heading over his shoulder. A document that historians will unearth much later, as an appendix to a book that no one here can have read, and which will be called Hitler’s Private Library.

We are recalled before the 2nd Armored Division comes back down toward the American zone. We leave behind a mountain that will change flags, a cellar being evacuated on stretchers, and thousands of books dispersing — into haversacks, under the stamp of the French, or at the bottom of a salt mine.

Beware, bibliophile friends, of the idea that great readers are great souls. I held the proof to the contrary in my hands, in a ruined house, on 4 May 1945. The binding was superb. The stroke beneath was that of a mediocre man.

We returned to our century on the morning of the 6th. The Fichte, for its part, is still running around somewhere, under a Cross of Lorraine stamp, from discreet sale to showcase of horror.

By Silas Deckard, traveller from the year 2125, temporal chronicler of the Guild of the Bibliopolicés, and Alcide Raturon, traveller of libraries — infiltrated in the uniform of the Régiment de marche du Tchad, 2nd Armored Division, Obersalzberg, May 1945.

IGLI-MS.T/1945-OBS-CG/04 Operation “Crayon Gris”. Visual record, Berghof. Source piece: Fichte, complete works, first edition, white vellum, one pencil underlining. Stamp 2e DB / G.5, Cross of Lorraine. Restricted access — Guild circulation.

P.S. — The bibliophilic elements of this report (the ~16,000 volumes spread across the residences, the 3,000 of the salt-mine depot, the ~1,200 kept at the Library of Congress, the Fichte given by Leni Riefenstahl, the 66 annotations in the Schertel, the Berlin guide by Max Osborn, the manner of underlining in pencil) come from: Timothy W. Ryback, Hitler’s Private Library: The Books That Shaped His Life, Alfred A. Knopf, New York, 2008 (French translation by Gilles Maurice-Dumoulin: Dans la bibliothèque privée d’Hitler. Les livres qui ont modelé sa vie, Le Cherche midi, 2009; reissued Le Livre de Poche, 2010). The stamp “collections personnelles d’Adolf Hitler / Berghof” of the G.5 section of the 2nd Armored Division, the Paul Gerbi sale (Vendée) and the Eagle’s Nest cellar come, for their part, from press and division archive sources.

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