KDP Gutter Margin Calculator —
Free Inside Margin Tool 2026

What Is the KDP Gutter Margin?

The gutter is the extra space added to the inside edge of each page — the side closest to the spine. When a paperback is bound, the pages curve inward toward the binding. Without enough gutter, the text near the spine gets swallowed into the fold and becomes difficult or impossible to read. Amazon KDP specifies exact minimum gutter requirements based on your total page count.

This is one of the most common reasons first-time self-publishers get their manuscripts rejected or receive poor-looking physical books. The required gutter is not the same as your outside, top, or bottom margins — it applies only to the inside edge of each page and must be mirrored correctly in your word processor or design software.

KDP Gutter Requirements by Page Count

How to Set Gutter in Microsoft Word

In Microsoft Word, gutter margin is set in the Page Setup dialog. Go to Layout → Margins → Custom Margins. In the Margins tab, find the “Gutter” field and enter your required gutter value. Set the “Gutter position” to Left. Make sure “Mirror margins” is selected so the gutter automatically alternates between left and right pages. This is essential for a properly bound book — without mirrored margins, the gutter only appears on one side.

How to Set Gutter in Adobe InDesign

In InDesign, create a new document with “Facing Pages” checked. Set your inside margin to your required gutter value. The inside margin applies to the right side of left-hand pages and the left side of right-hand pages — which is exactly what you need for a bound book. Make sure your document dimensions match your KDP trim size exactly before setting up margins.