Formatting
KDP paperback formatting: trim size, margins, bleed and a print-ready interior that passes review first time
Everything KDP checks in a paperback interior: choosing a trim size, calculating gutter margins from page count, bleed rules, fonts and embedding, spine width math and the errors behind most rejections.
KDP paperback formatting: trim size,
Formatting
Paperback formatting is where most first-time KDP publishers hit their first rejection email. The rules are mechanical — trim size, margins, bleed, embedded fonts — but they interact: your page count changes your gutter margin, your gutter changes your layout, and your layout changes your page count.
The good news is that the whole system reduces to a handful of numbers you can pin down before you format a single page. This guide gives you those numbers, the order to apply them in, and the specific errors that generate the majority of 'file issues' rejections.
It applies to standard black-ink nonfiction and fiction paperbacks. Children's books, heavy-image formats and hardcovers add rules, but the core mechanics below stay the same.
Pick the trim size first — everything else depends on it
Trim size is the physical page dimension, and 6 x 9 inches (15.24 x 22.86 cm) is the default for a reason: it suits most nonfiction and fiction, every tool has templates for it, and its printing cost per page is identical to smaller trims while fitting more words per page — which lowers total printing cost for the same manuscript.
Use 5 x 8 or 5.25 x 8 for shorter fiction where a thicker spine helps perceived value; 8.5 x 11 for workbooks and exercise-heavy layouts; square-ish trims for children's books. Once chosen, the trim is locked: changing it later reflows the entire book and invalidates your cover.
Decide ink and paper at the same time — black ink on cream paper is the classic fiction/nonfiction choice; white paper suits technical content; color ink multiplies printing cost several times and is rarely justified for text-driven books.
- 6 x 9 in is the safe default: cheapest path to fewer pages and universal template support.
- Page count drives printing cost: at ~$0.012 per page plus a fixed base, a 250-page book costs about $4 to print.
- Trim, ink and paper are locked together — decide them before formatting.
- Changing trim later means redoing interior and cover both.
Margins and the gutter: the page-count table that matters
KDP enforces minimum margins, and the inside margin (gutter) grows with page count because thicker books curve more at the binding. The minimums: outside, top and bottom at least 0.25 in without bleed (0.375 in with bleed); gutter at least 0.375 in up to 150 pages, 0.5 in for 151–300 pages, 0.625 in for 301–500 pages, 0.75 in for 501–700, and 0.875 in beyond.
Minimums are not recommendations. Text set at 0.25 in from the edge looks cramped and cheap; comfortable trade paperbacks run 0.5–0.75 in outside margins and a gutter one step above the legal minimum. Generosity here is the single cheapest upgrade to perceived quality.
Because gutter depends on page count and page count depends on layout, format in two passes: lay the book out with your best page-count estimate, check the final count against the gutter table, and adjust if you crossed a threshold.
- Gutter minimums: 0.375 in (≤150 p), 0.5 in (151–300), 0.625 in (301–500), 0.75 in (501–700).
- Outside/top/bottom: ≥0.25 in (no bleed) or ≥0.375 in (bleed).
- Set margins above the minimums for a professional feel.
- Two-pass formatting: layout → check page count against gutter table → adjust.
Bleed: when you need it and the exact math
Bleed lets images run to the trimmed edge of the page. Text-only books should publish without bleed — it simplifies everything. You need bleed only when images, color blocks or chapter-opener art must touch the page edge.
With bleed, the PDF page size grows by 0.125 in on the top, bottom and outside edges (not the gutter side): a 6 x 9 book becomes 6.125 x 9.25. Elements meant to bleed must extend fully to that enlarged edge; elements not meant to bleed must respect the normal margins.
The classic rejection here is a file declared 'with bleed' whose page size was never enlarged, or images stopping 1 mm short of the enlarged edge — both produce white slivers at the trim line and an automatic file-issue flag.
- No images touching page edges → publish without bleed.
- Bleed page size = trim + 0.125 in on three sides: 6 x 9 → 6.125 x 9.25.
- Bleeding elements must reach the enlarged edge completely.
- Declare bleed in KDP consistently with how the PDF was built.
Typography and the interior PDF: fonts, sizes, embedding
Body text in a serif face at 10.5–12 pt with 1.2–1.5 line spacing is the trade-book standard — Garamond, Palatino and similar faces read effortlessly in print. Reserve sans-serifs for headings and captions. Justify body text with hyphenation enabled, or accept the ragged-right look deliberately.
Front matter order is conventional and readers notice deviations: half-title, title page, copyright page, dedication, table of contents, then the body starting on a right-hand (odd) page. Running headers and page numbers skip display pages.
Export as PDF with all fonts embedded — unembedded fonts are a top rejection cause — images at 300 DPI, no crop marks, no password protection, and the exact page size discussed above. KDP's previewer then shows you precisely what the printer will produce; review every flagged page before approving.
- Serif body 10.5–12 pt, line spacing 1.2–1.5; sans for headings.
- Body starts on a right-hand page; display pages carry no headers or numbers.
- PDF: fonts embedded, images 300 DPI, no crop marks, no security.
- Always run KDP's previewer and resolve every warning before publishing.
Spine math and how the interior constrains the cover
The cover is a separate file, but the interior dictates its dimensions. Spine width = page count × 0.002252 in for white paper, or × 0.0025 in for cream. A 300-page cream book has a 0.75 in spine; the full wraparound cover is then back width + spine + front width, plus 0.125 in bleed on all four sides.
Spine text is only allowed at 100 pages or more, and it must fit with at least 0.0625 in clearance on each side — thin books simply leave the spine blank. Get the page count final before the cover is built; ten pages of late edits change the spine enough to misalign printed text.
This interlock is why finishing order matters: lock the interior, compute the spine, then produce the cover. Automated pipelines do this arithmetic for you — DraftToDone computes the wraparound dimensions from the actual final page count when it generates the print cover PDF — but the dependency exists no matter which tool builds the files.
- Spine = pages × 0.002252 in (white) or 0.0025 in (cream).
- Spine text requires ≥100 pages with clearance on both sides.
- Cover dimensions derive from the final interior — lock page count first.
- Late interior edits silently invalidate an already-built cover.
The short list behind most rejections
Almost every interior rejection traces to one of a handful of causes: text or page numbers inside the margin zones, fonts not embedded, page size not matching the declared trim (or bleed mismatch), images under 300 DPI flagged as blurry, and gutter too small for the page count.
Two non-file issues round out the list: a table of contents whose page numbers no longer match after final edits, and mismatch between the metadata (trim, page count) entered in KDP and the uploaded file.
Budget a careful previewer session as part of publishing, not as a reaction to rejection. Fixing issues before first submission keeps your title out of the review-resubmit loop that can add days to a launch.
- Top causes: margin violations, unembedded fonts, page-size mismatch, low-DPI images, undersized gutter.
- Verify TOC page numbers after the last edit, not before.
- Match KDP metadata exactly to the file: trim, bleed, page count.
- One previewer session before submission beats days of resubmission.
Operational checklist
- Trim size, ink and paper chosen before formatting began.
- Margins set above KDP minimums; gutter checked against final page count.
- Bleed decision made; page size enlarged to 6.125 x 9.25 (for 6 x 9) if bleeding.
- Serif body 10.5–12 pt, correct front-matter order, body starts on odd page.
- PDF exported with embedded fonts, 300 DPI images, no crop marks or security.
- Spine width computed from final page count; spine text only if ≥100 pages.
- Cover wraparound dimensions derived from the locked interior.
- KDP previewer run; every warning resolved before approval.
- KDP metadata (trim, bleed, page count) matches the uploaded file exactly.
FAQ
What is the best trim size for a KDP paperback?
6 x 9 in for most fiction and nonfiction: universal template support and more words per page, which means fewer pages and lower printing cost for the same manuscript. Choose differently only with a layout-driven reason — workbooks (8.5 x 11), short fiction (5 x 8), children's books (square trims).
Does KDP charge for printing, and how does formatting affect it?
Printing cost is deducted from each sale's royalty and scales with page count (roughly a fixed base plus about $0.012 per black-ink page). Tighter typography and a 6 x 9 trim reduce page count, directly raising your per-copy royalty.
Do I need bleed for a text-only book?
No. Bleed exists for images and color that touch the page edge. A text-only interior should be built and declared as no-bleed — it is simpler and removes an entire class of rejection errors.
Why was my interior file rejected?
The most frequent causes: content inside the required margins, fonts not embedded in the PDF, page size not matching the declared trim or bleed setting, images below 300 DPI, or a gutter too small for the page count. KDP's previewer flags each of these before submission if you let it.
Can I format a KDP paperback in Word?
Yes — set the page size to the trim, configure mirrored margins with the correct gutter, embed fonts when saving to PDF, and check the result in the previewer. Dedicated layout tools and automated pipelines produce more polished results, but Word output passes review when the numbers are right.