Choose the right trim size
Trim size is your printed book’s width and height. It decides how many pages your book runs to, what each copy costs to print, and whether it feels like a novel or a magazine in someone’s hand.
Pick two sizes below and see them at true relative scale.
How trim size affects what you earn
Two things move together, and only one of them is obvious.
A bigger page holds more words, so the same manuscript runs to fewer pages. Fewer pages is a lower per-copy print cost, because KDP charges a fixed amount plus an amount per page.
The part people miss is that the fixed and per-page amounts are not the same for every size. KDP splits trim sizes into regular and large, and large trims are priced on a different card. Their own words: books measuring more than 6.12 inches (155.5 mm) in width or more than 9 inches (228.6 mm) in height are large trim sizes and have different printing costs.
So going bigger to cut your page count can leave you worse off. 6.14″ × 9.21″ is the sharpest example on the list — it is fourteen hundredths of an inch over the line, and it pays large-trim rates for the privilege.
Run your actual trim, ink, paper and page count through KDP’s printing cost calculator before you commit. And once you have settled on a size and a page count, our spine width calculator gives you the cover dimensions that go with it.
The sizes readers expect
Genre convention is real and it is unforgiving. A thriller in 8.5″ × 11″ reads as a workbook on a shelf, and a picture book in 5″ × 8″ reads as a pamphlet.
| If you are writing | Use | Why |
|---|---|---|
| Fiction, most non-fiction | 6″ × 9″ | The default. Nobody will look twice at it, which is the point. |
| Novellas, poetry | 5″ × 8″ | Small enough to read as deliberate rather than thin. |
| Trade fiction, memoir | 5.5″ × 8.5″ | Slightly more intimate than 6 × 9 and the safest hardcover size. |
| Workbooks, manuals | 7″ × 10″ | Room for exercises, tables and wide figures. |
| UK workbooks and reports | 8.27″ × 11.69″ (A4) | The size UK readers and printers already expect. |
| Children’s picture books | 8″ × 10″ or 8.25″ × 8.25″ | Portrait or square, both conventional. |
| Read-across-the-spread picture books | 8.25″ × 6″ | Landscape, so the illustration runs across both pages. |
Watch the page ceiling
Every trim size has a maximum page count, and it changes with the paper. Most paperback sizes top out at 828 pages on black ink and white paper, but 8.5″ × 8.5″ and 8.5″ × 11″ stop at 590, and cream paper is always lower than white because the stock is thicker.
If you are writing something long, check the ceiling before you fall in love with a size. A 700-page manuscript rules out both the 8.5″ sizes entirely.
Hardcovers are stricter again: a minimum of 75 pages and a maximum of 550, on five sizes only.
Not sure which to choose?
publishing.co.uk defaults to the industry standard 6x9, but you can select any size at checkout.
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