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KDP spine width, cover size and margin calculator

Enter the trim size, page count and paper of your paperback. You get the spine width, the full cover size with bleed, the minimum inside and outside margins, and the Amazon.com printing cost, using the formulas on KDP's help pages.

US paperback rules from the KDP help pages, checked 29 October 2026. The numbers update as you type.

Interior PDF

Cover

Cover layout to scale: bleed (pink), back cover, spine and front cover, safe zones 0.125 in inside the trim (dashed). The barcode box is drawn about where KDP places it; KDP's own cover template shows the exact spot for your book.
Make the interior in Gridbinder

How the numbers are worked out

Spine width is the page count times the thickness KDP gives for each paper: 0.002252 in per page for white paper, 0.0025 in for cream, 0.002252 in for standard colour and 0.002347 in for premium colour. A 120-page book on white paper has a spine of 120 x 0.002252 = 0.2702 in.

Full cover width is bleed + back cover + spine + front cover + bleed, and the height is bleed + trim height + bleed. The bleed is 0.125 in on every side. For a 6 x 9 in book with 120 white pages that is 0.125 + 6 + 0.2702 + 6 + 0.125 = 12.5202 in wide and 9.25 in tall.

Inside margin (gutter) depends on the page count: 0.375 in for 24 to 150 pages, 0.5 in for 151 to 300, 0.625 in for 301 to 500, 0.75 in for 501 to 700 and 0.875 in for 701 to 828. Outside, top and bottom margins must be at least 0.25 in without bleed, or 0.375 in with bleed.

Page size for the interior PDF is the trim size when there is no bleed. With bleed it is 0.125 in wider and 0.25 in taller: a 6 x 9 in book becomes 6.125 x 9.25 in.

Printing cost on Amazon.com for black ink is a fixed $2.30 for 24 to 110 pages on a regular trim ($2.84 on a large trim), and $1.00 plus $0.012 per page from there ($0.017 per page on a large trim). A large trim is wider than 6.12 in or taller than 9 in. Your royalty is the rate times the list price minus printing: 50% at $9.98 or less, 60% at $9.99 or more.

The calculator is a planning aid. Before you upload, download KDP's own cover template for your exact trim, page count and paper, and check the interior in KDP's print previewer. If our number and KDP's differ, use KDP's and tell us at support@arling.sk.

Worked example: a 6 x 9 Sudoku book

In our test, 150 Sudoku puzzles at 6 x 9 in, two per page, with how-to pages, an answer key and a Verification report came to 109 pages in Gridbinder. KDP counts that as 110 pages. On white paper:

Spine: 110 x 0.002252 = 0.2477 in. That is over the 80-page line, so spine text is allowed, but a quarter of an inch leaves room for one short line only. Cover: 0.125 + 6 + 0.2477 + 6 + 0.125 = 12.4977 in by 9.25 in. Inside margin: at least 0.375 in (the studio used 0.5 in). Printing on Amazon.com: $2.30, because black-ink books of 24 to 110 pages pay only the fixed cost. At a list price of $7.99 the royalty is 50% x $7.99 minus $2.30, about $1.70 a copy.

What Gridbinder does with these rules

The studio builds the interior PDF, not the cover. It sets the page to the trim size (no bleed), keeps the top and outside margins at half an inch, and sets the inside margin from the final page count with an eighth of an inch more than the KDP minimum. When the book is ready it shows you the page count, which is the number you type into the KDP cover calculator or into the box above. Make a free sample to see it on your own settings.

Questions

Does KDP have its own spine width calculator?

Yes. KDP's cover calculator on kdp.amazon.com makes a cover template for your trim size, page count and paper. This page uses the same published formulas, adds the interior margins and printing cost in one place, and works without signing in.

How many pages do I need for text on the spine?

KDP prints spine text only on thicker books. One KDP help page says a book needs at least 79 pages for spine text, another says more than 79, and the cover page notes that Cover Creator needs 80. We use 80 to be safe. Keep the text at least 0.0625 in from each edge of the spine.

Do puzzle books need bleed?

Usually not. Bleed is only needed when something is printed to the edge of the page, such as a background colour or a photo. Puzzle grids sit inside the margins, so most puzzle books are set up without bleed and the page size equals the trim size. The cover always needs bleed.

Why does my page count change by one?

KDP counts pages in pairs. If your PDF has an odd number of pages, KDP rounds up to the next even number, and the calculator does the same.

Is cream or white paper better for a puzzle book?

Cream is only available with black ink and is thicker, so the spine is wider. White gives the most contrast for thin grid lines and small numbers, and it is the only option for colour. Both cost the same on Amazon.com for black ink.

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