Metric trim sizes, and books printed outside the US
Every trim size on a print-on-demand setup page is in inches: 5 x 8, 5.25 x 8, 5.5 x 8.5, 6 x 9. That is not a typographic judgment about the right shape for a page. It is where the industry grew up — print-on-demand was built in the United States, the templates were specified in inches, and the American trade sizes became the defaults by arriving first.
Most of the world buys books measured in millimeters. In the UK, Europe, Australia or India, the paperbacks on your own shelf are mostly not 6 x 9, and the sizes your readers recognize have different names.
The sizes the rest of the world uses
- A5 — 148 x 210 mm (5.83 x 8.27 in). Half an A4 sheet, and the ISO size used across Europe for nonfiction, manuals, workbooks and academic titles.
- B-format — 129 x 198 mm (5.08 x 7.80 in). The UK and Commonwealth trade paperback. Literary fiction and most novels are published at this size; it is what a British reader pictures when they picture a paperback.
- A-format — 111 x 178 mm (4.37 x 7.01 in). The older UK mass-market paperback, sold from racks rather than tables. A shrinking category, and a small page for a long book.
- Demy octavo — 138 x 216 mm (5.43 x 8.5 in). A traditional British and Commonwealth size, common for memoir and general nonfiction.
- Royal octavo — 156 x 234 mm (6.14 x 9.21 in). The larger UK and Australian trade size, used for hardbacks and serious nonfiction.
What they correspond to
Read across, and the metric sizes land close to trims you already have:
- Royal is roughly 6 x 9 — about 3.6 mm wider and 5.4 mm taller.
- Demy is roughly 5.5 x 8.5 — the height matches to within a tenth of a millimeter, and demy is about 1.7 mm narrower.
- B-format is roughly 5 x 8 — about 2 mm wider and 5 mm shorter.
- A5 has no close imperial twin. It is wider than 5.5 x 8.5 and shorter than it, which is why an A5 page looks like a different kind of object from a novel.
Those pairings are shelf judgments, not file instructions. A few millimeters is invisible in a reader's hand and fatal in a print file: a 6 x 9 cover submitted against a royal template is wrong at the spine and at both fore-edges, and a press does exactly what the file says.
A printer prints the sizes on its own list
This is the fact that decides the question for most authors. A print-on-demand company does not cut to whatever dimensions you name. It has a list — a set of trims, per binding — and a size that is not on it cannot be ordered at any price.
Those lists differ between companies, differ between paperback and hardcover, and change. Confirm the size in the printer's own current catalog before you design toward it; any guide, including this one, is out of date the moment a printer revises its list.
In the Cover Maker. Pick the printer, binding and trim and the wrap is measured to that printer's own specification — live trim, bleed and safe-area guides, and the spine computed from your real page count and paper color rather than from a rule of thumb. Start a book → · about the Cover Maker
Converting between metric and imperial re-flows the book
Moving a finished book from 5.5 x 8.5 to A5 is not a resize. The text block changes width, every line breaks in a new place, chapter openings land on new pages, and the total page count moves.
The page count is what makes that expensive. Spine width is derived from it, so a new page count means a new spine, a new wrap size, and spine text set for a space that no longer exists. A book already proofed needs proofing again from page one. Choosing a trim size covers why this is a decision to make once, going in.
Scaling is not a shortcut either. Printing a 6 x 9 interior at 96 percent to fill a royal page shrinks the type and pulls the text toward the gutter, the one direction margins must not go. See Margins and gutters.
Most books are printed at one size everywhere
Authors selling in several countries usually land in the same place: one trim, used in every market.
The reason is arithmetic rather than principle. A second trim is a second interior, a second page count, a second spine, a second cover file per binding, and a second proof — for every printer you use. A reader who wanted your book does not put it down because it is 6 x 9 rather than royal.
The case for a local size is real but narrow: a book aimed at one national market, sold mainly through shops there, where the shelf convention is strong and the buyer is a professional. A British literary novel at B-format is the clearest example.
How to decide
- Start from where the sales will be. If most copies will be bought online in the US, take a US trim and stop thinking about it.
- Check five comparable books in your main market. Printed dimensions are listed on most retail pages. If four of the five are B-format, that is the local convention, worth knowing even if you overrule it.
- Confirm the size exists at your printer, in your binding, before designing. Hardcover lists are shorter than paperback lists.
- Prefer a size every printer you might use can produce. A trim only one company offers ties your book to that company.
What we can tell you, and what we cannot
Four trims work on every printer supported here — 5 x 8, 5.25 x 8, 5.5 x 8.5 and 6 x 9 — across Amazon KDP, IngramSpark, Lulu and B&N Press, and across perfect bound paperback, case laminate hardcover and dust jacket.
Beyond those four, the size list belongs to each printer, and we name none of them. Metric availability varies by company, binding and region, and the only accurate answer is on the printer's current specification page the day you upload.
Make yours
Everything here is built into the tools, and they are free to use: name your book, bring your manuscript or your artwork, and work as long as you like. You only pay when you want the files without the preview watermark.
Next in this guide: Printing in more than one country · More: Choosing a trim size · Where to print: KDP, IngramSpark, Lulu and B&N Press · How to calculate spine width