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Gutter margin

Printing & file preparation

Also called: inside margin, binding margin

Extra inside margin that compensates for the part of the page swallowed by the binding. KDP's required gutter grows with page count, because thicker books open less flat.

When a book is bound, the inner edge of each page curves into the spine and some of it becomes physically hard to see. The gutter is the additional inside margin that keeps text out of that curve.

The amount needed depends on how thick the book is: a 60-page booklet opens nearly flat and needs little, while a 600-page volume needs substantially more. KDP publishes minimum gutter figures banded by page count, and a manuscript that passes at 200 pages can fail the same check after you add another hundred pages.

Gutter alternates sides. On a right-hand page the gutter is the left margin; on a left-hand page it is the right. Layouts that use a single symmetric margin for every page will be wrong on half of them — this is what mirrored or facing-pages margins in a layout program exist to handle.

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Related terms

  • Trim size

    The finished width and height of a printed book after the pages are cut. KDP publishes a catalog of standard trim sizes, and the one you pick affects both layout and printing cost.

  • Safe area

    The inset region of a cover or page where text and important artwork are guaranteed to survive trimming. On KDP covers it sits 0.125 inches inside the trim edge.

  • Interior paper

    The stock your pages print on — white, cream, or groundwood for black ink, and colour stock for colour interiors. It changes both the printing cost and the spine width.

  • Low-content book

    A book made mostly of repeating or generated page structures rather than prose — journals, planners, logbooks, and similar fill-in interiors.