Picking from the available KDP trim sizes is one of the earliest — and most consequential — decisions in self-publishing. Your trim size is the final, cut size of each printed page, and it shapes everything downstream: your margins, your page count, your printing cost, even how professional your book feels in a reader’s hands. Most debut authors default to 6 x 9 inches, and for many books that is genuinely the right call. But KDP supports more than a dozen trim sizes across paperback and hardcover, and the wrong choice can inflate your print costs, distort your layout, or make genre readers suspicious before they read a word.
Before we dig in: trim size is only one piece of a KDP-ready interior. If you are starting from scratch, our complete KDP formatting guide walks through the whole process from manuscript to print-ready PDF, and our guide to margins and typography explains how gutters and fonts should adapt to the size you pick.
Quick answer: For most novels and general nonfiction, 6 x 9 inches is the safest KDP trim size. Choose 5 x 8 or 5.5 x 8.5 for shorter books, 8.5 x 11 for workbooks and journals, and 8.5 x 8.5 with bleed for children’s picture books. Set the trim size before you format — KDP does not let you change it after publishing.
In this guide
- What Is a Trim Size, and Why Does It Matter?
- The Full List of KDP Paperback Trim Sizes (2026)
- KDP Hardcover Trim Sizes
- The Most Popular Trim Sizes by Genre
- How Trim Size Affects Page Count, Printing Cost, and Royalties
- Bleed vs. No-Bleed: What KDP Expects
- How to Set Your Trim Size in Word and InDesign
- Can You Change Your Trim Size After Publishing?
- Frequently Asked Questions
- Conclusion: Lock In Your Trim Size Early
What Is a Trim Size, and Why Does It Matter?
Your book’s trim size is the final, cut-down dimension of each printed page — the actual width and height of the book a reader holds. The name comes from the printing process itself: after pages are printed and bound, the book block is “trimmed” on three sides to its finished size.
Why does this one setting matter so much? Because nearly every other formatting decision flows from it. Margins and gutters are sized relative to the page; font size and line length are judged against it; page count — and therefore printing cost and royalty — is a direct function of how much text fits on each page. Set the trim size first, format second.
Trim size also sends a signal to readers. Book buyers are pattern-matchers: a 6 x 9-inch paperback says “novel or serious nonfiction,” while an 8.5 x 11-inch paperback says “workbook, journal, or textbook.” Choosing a trim size your genre does not expect will not get your book rejected by KDP — the platform accepts any of its supported sizes — but it can quietly tell browsers that the book inside was not made by someone who knows the category.
The Full List of KDP Paperback Trim Sizes (2026)
KDP currently supports 16 paperback trim sizes. Not every size is available in every marketplace, so double-check KDP’s help page for your market before you commit.
The sizes most self-publishers will ever need
- 5 x 8 in (12.7 x 20.32 cm)
- 5.25 x 8 in (13.34 x 20.32 cm)
- 5.5 x 8.5 in (13.97 x 21.59 cm)
- 6 x 9 in (15.24 x 22.86 cm)
- 6.14 x 9.21 in (15.6 x 23.39 cm)
Specialty and large-format sizes
- 5.06 x 7.81 in (12.85 x 19.84 cm)
- 6.69 x 9.61 in (16.99 x 24.41 cm)
- 7 x 10 in (17.78 x 25.4 cm)
- 7.44 x 9.69 in (18.9 x 24.61 cm)
- 7.5 x 9.25 in (19.05 x 23.5 cm)
- 8 x 10 in (20.32 x 25.4 cm)
- 8.25 x 6 in (20.96 x 15.24 cm) — a landscape option
- 8.25 x 8.25 in (20.96 x 20.96 cm)
- 8.27 x 11.69 in (21 x 29.7 cm) — A4
- 8.5 x 8.5 in (21.59 x 21.59 cm)
- 8.5 x 11 in (21.59 x 27.94 cm)
Two practical notes. First, paperback manuscripts must be between 24 and 828 pages; if your book falls outside that range, the trim size is not the problem. Second, the more unusual sizes (like 5.06 x 7.81 and 6.69 x 9.61) exist mainly to mirror traditional publishing standards. Unless you have a specific reason, the five sizes in the first list will cover nearly every self-publishing project.
KDP Hardcover Trim Sizes
Hardcover is pickier. KDP supports only nine hardcover trim sizes, and your manuscript must run between 75 and 550 pages to qualify:
- 5.5 x 8.5 in (13.97 x 21.59 cm)
- 6 x 9 in (15.24 x 22.86 cm)
- 6.14 x 9.21 in (15.6 x 23.39 cm)
- 7 x 10 in (17.78 x 25.4 cm)
- 8.25 x 8.25 in (20.96 x 20.96 cm)
- 8.25 x 11 in (20.96 x 27.94 cm)
- 8.27 x 11.69 in (21 x 29.7 cm)
- 8.5 x 8.5 in (21.59 x 21.59 cm)
- 8.5 x 11 in (21.59 x 27.94 cm)
If you plan to release paperback and hardcover editions of the same book — which most serious authors should — choose a trim size that appears on both lists. 6 x 9, 5.5 x 8.5, and 6.14 x 9.21 are the natural crossover picks for text-driven books; 8.5 x 8.5 and 8.5 x 11 cover illustrated and workbook-style titles. Build the hardcover interior after the paperback one so you can reuse the text flow and only adjust the margins for case binding.
The Most Popular Trim Sizes by Genre
Knowing the full list is useful; knowing what readers expect is more useful. Here is how trim size conventions break down by genre.
Fiction and general nonfiction. 6 x 9 inches is the undisputed standard for novels, memoirs, business books, and self-help. It is the size of most traditionally published trade paperbacks, and readers never notice it — which is exactly the point. 5.5 x 8.5 is the main alternative: slightly more intimate, common in literary fiction and memoir.
Romance, novellas, and poetry. Shorter books feel lost at 6 x 9. Romance publishers favor 5 x 8 and 5.25 x 8, which make a 200-page book feel substantial in the hand. Poetry collections and gift books use the smaller sizes for the same reason: perceived value.
Children’s picture books. 8.5 x 8.5 inches with full bleed is the KDP standard, with 8.25 x 8.25 as the alternative. Square formats display illustrations well and sit comfortably on a child’s lap.
Workbooks, journals, and planners. 8.5 x 11 inches — US Letter — dominates because readers expect room to write. 7 x 10 and 8 x 10 are common when authors want a slightly less bulky feel.
Cookbooks, photography books, textbooks, and manuals. 7 x 10, 7.5 x 9.25, and 8.5 x 11 suit image-heavy layouts; 8.27 x 11.69 (A4) or 8.5 x 11 suit textbooks, usually with generous margins for notes.
6.14 x 9.21 deserves a special mention: it is the “US trade” size many traditional publishers use, and a growing number of self-publishers choose it to look indistinguishable from traditionally published books.
How Trim Size Affects Page Count, Printing Cost, and Royalties
Trim size is a cost lever, and most authors never touch it. Here is the math.
Page count. For a fixed word count, a smaller trim size means fewer words per page, which means more pages. A 70,000-word novel might run 280 pages at 6 x 9 but 330 pages at 5.5 x 8.5 — the same book, 50 extra pages, purely from the trim setting.
Printing cost. KDP charges a printing cost for every paperback sold, calculated as a fixed cost plus a per-page cost (the exact figures vary by marketplace, ink type, and trim size — check KDP’s current print-cost table before you finalize pricing). Those extra 50 pages add real money to every unit: each additional page costs roughly a cent in the US market. On a book that sells thousands of copies, a careless trim choice can quietly eat hundreds of dollars in royalties.
Royalties. Your paperback royalty is 60% of the list price minus the printing cost (40% for Expanded Distribution). Because printing cost rises with page count, and page count rises as trim size shrinks, a smaller trim size squeezes your royalty — unless you raise the list price, which can hurt conversion.
The practical takeaway: do not pick a tiny trim size for a long book just because it looks elegant. Run the numbers. For most text-driven books, 6 x 9 hits the sweet spot — enough words per page to keep printing costs down, standard enough that readers accept the list price it supports.
Bleed vs. No-Bleed: What KDP Expects
“Bleed” means printed content — usually images or background color — runs all the way to the edge of the page, past the trim line. The printer deliberately prints slightly oversize and trims the excess, so there is no white sliver at the edge.
KDP’s rule is precise: any artwork that touches the edge of the page must extend 0.125 inches (3.2 mm) beyond the trim line on every side that bleeds. So a full-bleed 8.5 x 8.5-inch interior must actually be built at 8.75 x 8.75 inches. If only some pages bleed, you still set the entire PDF to the bleed dimensions — KDP requires one consistent page size for the whole file.
When should you choose bleed? Picture books, children’s books, cookbooks, photography books, and any workbook with full-page background designs need it. Standard text-driven books — novels, memoir, business nonfiction — should use no-bleed, where the PDF page size equals the trim size exactly and all content stays inside the margins.
The most common bleed mistake is partial bleed: an image that almost reaches the edge but stops a hair short. That hair becomes a visible white line after trimming. If an element goes to the edge, push it a full 0.125 inches past; if it does not, keep it well inside the safe margin.
How to Set Your Trim Size in Word and InDesign
In Microsoft Word
Go to Layout, then Size, then More Paper Sizes. Enter your trim dimensions as the custom width and height (for 6 x 9, width 6 inches and height 9 inches), and — critically — set Multiple pages to “Mirror margins” so Word creates proper inside (gutter) and outside margins. Add extra gutter width (0.25 to 0.5 inches depending on page count) so text does not disappear into the binding. Do this before you type a single chapter heading; retrofitting a trim size into a finished manuscript is where most layout disasters start.
In Adobe InDesign
Choose File, then New, then Document. Enable Facing Pages, set the page size to your trim dimensions, make the inside margin larger than the outside margin to reserve the gutter, and build on master pages so every chapter inherits the same geometry.
Whichever tool you use, export the interior as a print-ready PDF with fonts embedded and the page size matching your trim choice exactly (or trim plus bleed, if applicable). Then confirm that the trim size selected in the KDP dashboard matches the PDF’s page dimensions. A mismatch — say, a 6 x 9 PDF uploaded against a 5.5 x 8.5 selection — will fail KDP’s file review and send you back to square one.
Can You Change Your Trim Size After Publishing?
Short answer: no — not on a live book. KDP locks the trim size once your book is published; you cannot edit it the way you can tweak a description or a price.
If you published at the wrong trim size, your only path is to unpublish the book and republish it as a new title with the corrected trim size. That new edition needs a new ISBN, and — this is the painful part — it starts with zero reviews, zero sales rank, and zero Also Bought history. Your old edition’s social proof does not transfer.
This is why trim size belongs at the very top of your pre-publication decisions, alongside your title and ISBN. It is a one-way door. Before you click publish, run through our pre-publish checklist and verify these three things:
- The trim size selected in your KDP dashboard
- The page dimensions of your uploaded interior PDF
- Your cover file’s dimensions (built for the same trim size, spine width included)
Thirty seconds of verification now saves you from rebuilding and relaunching a book later.
Frequently Asked Questions
Conclusion: Lock In Your Trim Size Early
Your KDP trim size is a one-way decision that shapes your layout, your printing cost, and your royalty on every copy sold. For most authors, 6 x 9 inches is the right answer; for illustrated or write-in books, go bigger and add bleed where the genre expects it. Set the size before you format and match it exactly in your PDF and cover, and you will never have to think about it again.
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