KDP Margins and Gutter, by Page Count
KDP's minimum inside (gutter) and outside margins for every page-count band — and why the gutter you need depends on a page count the gutter itself changes.
The published minimums
KDP sets one margin by page count and three by a flat rule. The inside margin — the gutter, against the spine — grows as the book thickens, because a thicker text block curls further into its own binding. The outside, top and bottom minimums do not move with page count, but they do move if the interior uses bleed.
| Page count | Inside (gutter) | Outside, top, bottom | Outside, with bleed |
|---|---|---|---|
| 24–150 pages | 0.375" (9.6 mm) | 0.25" (6.4 mm) | 0.375" (9.6 mm) |
| 151–300 pages | 0.5" (12.7 mm) | 0.25" (6.4 mm) | 0.375" (9.6 mm) |
| 301–500 pages | 0.625" (15.9 mm) | 0.25" (6.4 mm) | 0.375" (9.6 mm) |
| 501–700 pages | 0.75" (19.1 mm) | 0.25" (6.4 mm) | 0.375" (9.6 mm) |
| 701–828 pages | 0.875" (22.3 mm) | 0.25" (6.4 mm) | 0.375" (9.6 mm) |
Two things about this table are worth saying out loud, because both are routinely dropped elsewhere.
The 24 and 828 at the ends of the range are the book, not the table. KDP does not print a paperback below 24 pages or above 828, so a band outside those numbers does not exist rather than defaulting to the nearest one.
Bleed raises the outside minimum from 0.25" to 0.375". Most summaries quote the 0.25" figure flat and never mention that turning bleed on moves it. It moves because the outside edge is the edge being cut: content sized to a 0.25" outside margin on a bleed interior is sitting inside the trim variance, not clear of it.
Your margins, for one book
The table above is the whole rule; this is it applied to your book. It also flags the case the next section is about — a page count sitting close enough to a band edge that setting the margin can push you over it.
- Inside (gutter), minimum
- 0.5"
- Outside, top, bottom
- 0.25"
- Band
- 151–300 pages
- Text block width
- 5.25"
Minimums, not recommendations — going wider is always allowed, going narrower is not. Figures are KDP's published interior margins; the table above this tool is the full set.
The part that catches people out
The gutter you need depends on your page count. Your page count depends on how much text fits on a page. How much text fits on a page depends on the width of the text block — which is the trim width minus the gutter and the outside margin.
That is a circle, and it is not academic. Widening the gutter narrows every line, which lengthens the book, which can push it over a band threshold into a gutter requirement wider still. A manuscript that lands at 298 pages with a 0.5" gutter is not safely inside the 151–300 band: set that gutter, re-flow, and it may come out at 304 — where KDP now wants 0.625".
The bands are hard edges, not gradients. There is no rounding in your favour at 301 pages.
The way out is to solve it rather than guess at it: pick a gutter, re-flow, check which band the resulting count lands in, and repeat until the band you assumed and the band you landed in agree. It usually settles in two passes. Our word count to page count calculator runs exactly that loop — it re-picks the gutter band on each pass until the count stops moving, which is why its estimate shifts when you cross a threshold.
Where this bites hardest: fixed-width interiors
Prose absorbs a margin change. A narrower text block re-flows, the book gets a few pages longer, and nothing looks wrong. A grid does not re-flow. A puzzle, a table, a music stave, or a wide code listing is a fixed-width object: if the text block narrows below its width, it does not get taller, it gets scaled down or clipped.
So on a puzzle or activity interior the margin decision has to come before the grid decision, not after. Work out the worst-case gutter for the page count you are aiming at, subtract it and the outside margin from the trim width, and design the grid to the width that survives — see the trim size guide for what each trim leaves you.
Checking a finished file
Two facts make the final check different from the planning one. First, KDP's page count comes from the file you upload, rounded up to an even number — every leaf has two sides — so the count your word processor reports is not necessarily the one that picks your band. Second, front matter counts: title page, copyright page and contents are pages like any others.
Once the PDF exists, measure it rather than trusting the export dialog. Our KDP interior PDF checker reads the real page geometry out of the file — including whether bleed was applied the way KDP asks, which is the other half of this page's subject and a common way for a correctly-margined interior to still come back rejected.
Common questions
Frequently asked questions
What is the gutter margin on KDP?
The gutter is the inside margin — the one against the spine. KDP requires it to be wider than the other three because a bound book curls into its own spine, and text set too close to the fold disappears into the binding. It is the only margin whose minimum changes with page count.
What gutter margin do I need for my page count?
KDP publishes five bands: 24–150 pages needs 0.375"; 151–300 pages needs 0.5"; 301–500 pages needs 0.625"; 501–700 pages needs 0.75"; 701–828 pages needs 0.875". The band is decided by the page count of the PDF you actually upload, not by your manuscript's word count.
Are the outside, top, and bottom margins the same as the gutter?
No, and they do not change with page count. Without bleed the minimum is 0.25" on the outside, top, and bottom. With bleed that minimum rises to 0.375" — a detail a lot of write-ups omit, because they quote the no-bleed figure flat.
Does turning bleed on change anything besides the margin?
Yes — it changes the page size too, and the two are separate requirements. KDP's rule is asymmetric: a bleed page is 0.125" wider and 0.25" taller than trim, because bleed extends the top, the bottom, and the outside edge, but never the gutter edge, which is bound. A 6 x 9 book with bleed is a 6.125 x 9.25 page.
Can adding pages change my required gutter?
Yes, and this is the trap. The bands are hard thresholds: a 300-page book needs 0.5" and a 302-page book needs 0.625". Because a wider gutter narrows the text block, it can push the page count up — sometimes across the very threshold that widened it. Set the gutter for the count you expect to end at, then re-check the count after you have set it.
Do these minimums apply to low-content and puzzle books?
Yes. The margin table is a manufacturing requirement, not a genre rule, so it applies to a puzzle interior exactly as it does to a novel. It bites harder on puzzle books, though, because a grid is a fixed-width object: prose reflows into a narrower text block, and a 15x15 word search does not.
Are these margins minimums or recommendations?
Minimums. KDP will reject or flag an interior that violates them, and meeting them exactly is legal but tight — most designers set the gutter above the minimum for comfort. Going wider is always allowed; going narrower is not.
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