Gutter
Also called: gutter margin, inside margin
Definition
The gutter is the inside margin near the spine where two facing pages meet. KDP requires a minimum gutter margin that scales with page count: 0.375 inch for 24 to 150 pages, 0.5 inch for 151 to 400 pages, and 0.625 inch for 401+ pages. Putting critical art in the gutter leaves it hidden in the spine.
What is the gutter in a KDP coloring book?
The gutter is the strip of inside margin closest to the spine on each page. When a paperback is bound, the gutter area curves into the spine and is partially hidden when the book lies open. Art placed in the gutter cannot be colored because the book will not lie flat enough.
Why does the gutter matter for coloring books?
A coloring book is meant to be opened flat and colored on. If line art extends into the gutter, the colorist cannot reach those parts of the illustration without breaking the spine. Many beginner publishers center their full-bleed art on the page and end up losing 0.5 inch of every illustration to the gutter.
What is the minimum gutter margin on KDP?
KDP scales the minimum gutter margin to page count. For 24 to 150 pages the minimum is 0.375 inch. For 151 to 400 pages it is 0.5 inch. For 401 to 600 pages it is 0.625 inch. Going below the minimum is one of the more common pre-flight rejection reasons.
How should a coloring book handle the gutter?
The safe pattern is to keep all line-art elements at least 0.5 inch from the spine edge, regardless of KDP's stated minimum. That gives the colorist a usable surface and avoids both rejection and reader complaints. For double-page spreads, mirror the design so that the gutter area is intentionally a low-detail break in the composition.
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Related terms
Bleed
Bleed is the 0.125 inch (3.2 mm) extension of artwork past the trim line of a KDP paperback page. It exists so that small variations in the cutting machine do not produce a thin white sliver at the page edge. Coloring books with full-page line art must include bleed or risk KDP rejection.
Trim size
Trim size is the final physical dimensions of a KDP paperback after cutting, measured in inches (US) and rounded to 0.001 inch. The most common KDP coloring book trim sizes are 8.5 x 11 inches (standard letter), 8 x 10 inches (compact), and 8.5 x 8.5 inches (square). Trim size is set at title creation and cannot change later.
Manuscript
The manuscript is the interior PDF file uploaded to KDP, distinct from the cover file. For coloring books, the manuscript contains all the line-art pages, any front matter (title page, copyright), and any back matter (about the artist, also-by). KDP requires a print-ready PDF at 300 DPI with embedded fonts and bleed.
Interior
The interior is the full set of inside pages of a KDP paperback, distinct from the cover. KDP interior options for coloring books include white or cream paper, black-and-white or color printing, and standard or premium paper weight. Coloring book interiors almost always use white paper with black-and-white printing.