Spine
Also called: book spine, spine width
Definition
The spine is the bound edge of a paperback, including the visible spine strip on the cover. Spine width is calculated from page count: KDP's formula is page count x 0.002252 inch for white interior paper, x 0.0025 inch for cream. A 100-page coloring book has a 0.2252 inch spine on white paper.
What is the spine on a KDP paperback?
The spine is the bound edge of the printed book. On the cover file, the spine occupies a vertical strip between the back cover (left) and the front cover (right) when the cover is laid flat. The spine width must match the calculated value for the manuscript's page count, or the cover will misalign during binding.
How is spine width calculated?
KDP's published formula for paperback spine width is: page count multiplied by 0.002252 inch for white interior paper, or 0.0025 inch for cream interior paper. A 60-page coloring book on white paper has a 0.135 inch spine. A 120-page coloring book has a 0.270 inch spine.
When can the spine carry text?
KDP allows spine text only on books with 80+ pages. Below that, the spine is too narrow to safely contain readable text without risking shift during printing. Coloring books often sit at 50 to 80 pages, which means many do not get spine text. Books at 100+ pages can carry the title and author name on the spine.
Why do spines come out crooked?
Crooked-spine complaints in reviews almost always trace to one of three root causes: spine width calculated for the wrong page count, cover artwork that flows across the spine without enough safety margin, or KDP's stated +/- 0.0625 inch print tolerance on the spine fold position. Designers add at least 0.125 inch of "do not cross" safety on each side of the spine fold.
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Related terms
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.
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.
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.