Paperback margin guide

KDP Gutter Size: How Much Inside Margin Does Your Book Need?

Last reviewed: October 2026

Short answer

KDP’s minimum gutter—the inside margin nearest the spine—depends on the final interior page count. Use 0.375" for 24–150 pages, 0.5" for 151–300, 0.625" for 301–500, 0.75" for 501–700, and 0.875" for 701–828 pages.

Current KDP minimum inside margins
Page Count	Minimum Inside Margin / Gutter
24–150 pages	0.375"
151–300 pages	0.5"
301–500 pages	0.625"
501–700 pages	0.75"
701–828 pages	0.875"

Current minimum outside margins: 0.25" for interiors without bleed and 0.375" for interiors with bleed. KDP applies the outside minimum to the top, bottom, and outer edge.

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KDP gutter calculator

Use the final page count from your interior PDF—not the page count in your editing document.

How many pages is your book?

Example: 347

Your minimum KDP inside margin:0.625"

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KDP Gutter Size by Page Count

Use the page count in the finished interior PDF, including front matter and intentional blank pages. KDP increases the minimum inside margin at 151, 301, 501, and 701 pages because thicker books need more room near the binding.

The figures above are minimum manufacturing requirements from Amazon KDP’s official trim, bleed, and margin guidance. A specific ink, paper, and trim combination may have a lower maximum page count than 828.

What Is the Gutter?

The gutter is the inside edge of each page—the edge closest to the spine and binding. On a left-hand page, the inside margin is on the right. On a right-hand page, the inside margin is on the left. Mirrored margins make those positions alternate automatically.

Open-book diagram: the two highlighted inside margins sit on either side of the spine—right edge of the left page and left edge of the right page.

Example: 350-Page KDP Paperback

Minimum inside margin: 0.625"

A 350-page paperback falls within the 301–500-page tier. If its interior does not use bleed, the minimum outside margin is 0.25". Those are minimums; the final design may use more space for comfort and balance.

Does Trim Size Change the Required Gutter?

The KDP minimum-gutter table is based on page count, not trim size. Trim size still matters indirectly: changing from 6×9 to 5×8 changes the available line length, which can change pagination. If the new page count crosses a threshold, the required gutter changes too.

Does Bleed Change the Gutter Size?

Bleed does not directly change the inside-margin tier. It changes the minimum outside margin: 0.25" without bleed and 0.375" with bleed. Bleed is needed when an image or background reaches a trimmed edge; ordinary text-only interiors usually use no bleed. For the complete outside, top, and bottom rules, see the KDP margin requirements guide.

A Common Gutter Mistake

A common mistake is giving the inside and outside edges the same margin. The binding side often needs more space than the outer edge, especially as the book becomes thicker.

Another mistake is setting the gutter before pagination is final. Changing the font, type size, line spacing, front matter, chapter starts, or trim size can change the page count and push the book into a larger gutter tier. Recheck the gutter after every change that repaginates the book.

What About Microsoft Word?

Use Word’s Mirror margins option so the inside and outside positions alternate correctly on facing pages. Enter the required binding-side space once.

Avoid counting the gutter twice.Some Word setups expose both an Inside margin and a separate Gutter field. If your Inside value already equals the full required KDP inside margin, adding the same amount again in Gutter makes the binding margin unnecessarily large.

Minimum Doesn’t Always Mean Ideal

KDP’s values are minimum manufacturing requirements, not a promise that the smallest possible margins will create the best-looking page. Genre, trim size, typography, line length, and book thickness all affect visual balance. A professionally designed book may use a larger inside, outside, top, or bottom margin than KDP requires.

Let Typeset Ready Handle the Book Setup

Upload a DOCX or .TXT manuscript, choose your book settings, preview the formatted interior, and export the finished publishing files. Typeset Ready recalculates pagination and applies the appropriate inside-margin tier to the book setup.

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Before Uploading Your Interior to KDP

Confirm the final page count
Check the inside / gutter margin
Check the outside margin
Confirm the trim size
Confirm the bleed setting
Review every chapter start
Check page numbers
Check headers and footers
Review intentional blank pages
Confirm fonts are embedded
Inspect the final PDF in KDP Print Previewer

Quick answers

Frequently Asked Questions

What gutter should I use for a 200-page KDP book?

The minimum inside margin is 0.5".

What gutter should I use for a 300-page book?

The minimum remains 0.5" through page 300.

What happens at 301 pages?

The minimum inside margin increases to 0.625".

What gutter should I use for a 400-page paperback?

The minimum inside margin is 0.625".

What gutter should I use for a 500-page book?

The minimum is 0.625". At 501 pages, it increases to 0.75".

Is the gutter the same as the inside margin?

Yes. KDP uses “inside margin” and “gutter” for the binding-side margin closest to the spine.

Does a 6×9 book need a special gutter?

No separate 6×9 gutter table applies. Use the final page count to select the minimum tier, then consider whether the design needs more than the minimum.

Official source: Amazon KDP — Set Trim Size, Bleed, and Margins. Requirements can change, so verify the final file in KDP Print Previewer before publication.