Margins are the keep-everything-inside lines around your text. KDP's minimums sound simple until you hit the one rule nobody warns you about: the inside margin — the gutter, the edge where pages are bound together — is not one number. It scales with your page count, because a thick book curves harder into its binding, and text set too close to the spine disappears into that curve.
What KDP is actually saying
KDP's published minimum margins for paperbacks:
| Page count | Inside (gutter) | Outside — no bleed | Outside — with bleed |
|---|---|---|---|
| 24–150 pages | 0.375″ | at least 0.25″ | at least 0.375″ |
| 151–300 pages | 0.5″ | at least 0.25″ | at least 0.375″ |
| 301–500 pages | 0.625″ | at least 0.25″ | at least 0.375″ |
| 501–700 pages | 0.75″ | at least 0.25″ | at least 0.375″ |
| 701–828 pages | 0.875″ | at least 0.25″ | at least 0.375″ |
Top and bottom margins follow the same minimums as the outside margin. Three things in that table trip people up:
- The gutter is per-book, not per-template. A template built for a 140-page book uses a 0.375″ gutter. Reuse it on a 320-page book and you're 0.25″ short — rejection. Growing your book across a tier boundary (say, edits push you from 148 to 155 pages) changes your gutter too.
- The gutter flips sides. It's always on the binding edge: the left of right-hand pages, the right of left-hand pages. Layout tools call this mirrored or facing-page margins. Set the same margins on every page and half your book has the wide margin on the wrong side.
- “Important elements” means more than body text. Page numbers, running headers, footnotes, and images all count. A page number sitting 0.2″ from the bottom edge triggers this error all by itself, even when every paragraph is perfect.
And a wise cushion: these are minimums, not targets. Setting your gutter 0.125″ above the minimum costs you nothing and buys insurance against rounding and reflow.
Check it yourself
- Get your final page count from the exported interior PDF — not the document you started with.
- Look up your gutter in the table above.
- Measure real pages. In your layout tool, turn on rulers and guides, and measure from the trim edge to the nearest text — on a left-hand page and a right-hand page, because the gutter side flips.
- Check the sneaky spots: page numbers, headers, footnotes, wide tables or images, and chapter-opening pages, which often use different spacing from the rest of the book.
Don't want to measure this yourself? Send us your interior and cover files and we'll run the full 13-point check — margins, bleed, spine, fonts, all of it — and tell you in plain English what's wrong. The check is free. Get the free check →
How to fix it
In Word
Layout > Margins > Custom Margins. First set Multiple pages: Mirror margins — that turns “left/right” into “inside/outside.” Then set Inside to your table value (plus a cushion), and Outside, Top, and Bottom to at least 0.25″ — or 0.375″ if your book uses bleed. Check where your page numbers live: if they're in the footer, make sure the footer distance keeps them inside the bottom margin.
In Pages (Mac)
Turn on Facing Pages in the Document sidebar, then set the inside and outside margins there — Pages mirrors them correctly for you. Set the values from the table, again with a small cushion above the minimum.
In Canva
Honest warning: Canva has no automatic mirrored margins. Turn on File > View settings > Show margins, keep every text box inside them, and remember you'd have to alternate the wide gutter side by hand, page by page. For a short picture book that's survivable; for a 300-page interior it's misery, and a word processor will treat you better.
In InDesign
Build the document with facing pages, then Layout > Margins and Columns: set Inside from the table, Outside/Top/Bottom to the minimums or better. Apply to the parent pages so chapter pages inherit it too.
The honest limit
Widening margins reflows the whole book — lines break differently, pages get longer or shorter, and your page count changes. That can move you into a different gutter tier, and it always changes your cover's spine width. So the order of operations matters: fix margins in the source document, re-export, recount the pages, then rebuild the cover. A finished PDF alone can't fix this one — text inside a PDF can't be reflowed, only moved or shrunk, and both look wrong. This is a source-document fix, and your free check will tell you plainly if that's where you stand.
Or send us the files — the check is free
Email your interior and cover PDFs and we'll tell you exactly what's wrong — in plain English, free, within 48 hours. If it does need fixing, the by-hand fix is $19 and we redo it free if KDP rejects it for a formatting issue we were hired to fix. We rebuild files to be compliant with KDP's published spec — that's the promise we can keep.