Pick your trim size, page count, and paper to get the spine width and the exact full-cover size KDP expects for a paperback, with bleed, in inches, millimetres, and pixels.
How it works
A KDP paperback cover is one flat image: the back cover, the spine, and the front cover side by side, with 0.125 in (3.2 mm) of bleed on the top, bottom, and outside edges. The spine width comes from the page count times the paper thickness KDP publishes: 0.002252 in per page for white paper (and standard colour), 0.0025 in for cream, 0.002347 in for premium colour.
Formulas: Spine = Pages x per-page thickness; Cover width = 0.125 + Trim width + Spine + Trim width + 0.125; Cover height = 0.125 + Trim height + 0.125. A 300-page 6 x 9 book on white paper has a 0.676 in spine and a 12.926 x 9.25 in cover, which is 3,878 x 2,775 pixels at 300 DPI.
Hardcover case-laminate covers are a different template: the printed sheet wraps around the boards and adds hinge and wrap allowances that KDP publishes only through its own cover calculator, so use that for a hardcover and this page for paperbacks. KDP prints no spine text under 80 pages, so keep the spine blank on short books.
Advanced options let you enter a custom trim width and height when the Trim size menu is set to Custom trim.
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Frequently asked questions
What size should my KDP cover be?
Exactly the full-cover size the calculator shows for your trim, page count, and paper, exported as a single PDF page at 300 DPI with the bleed included. For a 6 x 9 book of 300 pages on white paper that is 12.926 x 9.25 inches. KDP rejects covers whose page size does not match the trim and spine it expects for the book.
How do I calculate the spine width for KDP?
Multiply the page count by the paper thickness: 0.002252 inches per page for white paper, 0.0025 for cream, 0.002347 for premium colour, 0.002252 for standard colour. Use the page count of the interior PDF you upload, not the number printed on the last page. The spine text has to sit inside that width with a little margin on each side; KDP prints spine text only on books of 80 pages or more.
What are the KDP trim sizes?
Sixteen standard sizes from 5 x 8 to 8.5 x 11 inches (plus A4 at 8.27 x 11.69), all in the menu above, and custom sizes between 4 x 6 and 8.5 x 11.69 inches. 6 x 9 is the most common for novels and non-fiction, 5.5 x 8.5 and 5.25 x 8 for shorter fiction, 8.5 x 11 for workbooks and low-content books, and the square sizes for children's books.
What is bleed and do I need it?
Bleed is the 0.125-inch strip outside the trim that is cut off after printing, so colour and images that reach the edge of the cover do not leave a white sliver if the cut wanders. Every KDP cover PDF must include it, which is why the full-cover size is a quarter inch wider and taller than two trims plus the spine. Keep text and logos at least 0.25 in inside the trim edge.
Does this work for hardcover books?
No. KDP hardcovers are case laminate: the printed sheet wraps around rigid boards and needs hinge and wrap allowances on top of the trim and spine, and KDP publishes those only through its own cover calculator and downloadable template. Use that for hardcover files. The paperback formula here is the one KDP publishes in its paperback cover guidelines.
What resolution and file type does KDP want?
A single-page PDF at 300 DPI (the pixel sizes above are at 300 DPI), PDF/X-1a preferred, colour in CMYK or sRGB, fonts embedded, no crop marks, and the page size equal to the full-cover size with bleed. The Image Resizer can size a flat JPG or PNG to the pixel dimensions if your cover is a single image.