How do you calculate spine width for a KDP paperback?

Multiply your page count by the paper factor: 0.002252 inches per page for black ink on white paper, or 0.0025 inches per page for black ink on cream paper. A 120-page book on white paper has a spine of 0.27 inches.

What size should my KDP cover file be?

Full wrap width equals your trim width doubled, plus the spine width, plus 0.25 inches of bleed. Full wrap height equals your trim height plus 0.25 inches. A 6x9 book of 120 pages on white paper needs a cover 12.52 by 9.25 inches.

Can I put text on the spine of my book?

Amazon KDP only prints spine text on books with more than 79 pages. Below that the spine is too narrow and binding drift would wrap the text onto the front or back cover.

KDP Spine Width Calculator & Cover Template Generator

Enter your trim size, page count and paper stock. You'll get your exact spine width, the full wrap cover dimensions in inches and pixels, the interior gutter Amazon will require — and a blank template you can design over. Free, instant, no signup.

Trim size

Page count

Paper & ink

Spine width

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Full cover size

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includes 0.125" bleed all round

At 300 DPI

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canvas size for Canva / Photoshop

Interior gutter required

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inside margin at this page count

Outside margins minimum

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top, bottom & outer edge

Or use a ready-made cover template →

The blank template marks trim, bleed, spine folds, safe area and the barcode keep-out — open it in Canva at exactly the pixel size above and design on top. Prefer not to design at all? The Studio has four finished cover templates in five colourways, and it works the spine out from your book automatically. Free to use and export; a small credit on the back cover is removed with Pro.

How KDP spine width is calculated

Amazon doesn't publish a spine width for your book — it expects you to work it out, and gets it wrong at your peril. The formula is simply page count multiplied by a per-page paper thickness:

Paper & ink	Inches per page	Example: 120 pages
Black ink, white paper	`0.002252`	0.2702"
Black ink, cream paper	`0.0025`	0.3000"
Premium colour, white paper	`0.002347`	0.2816"

Note that cream paper is thicker than white. Switching paper stock after you've made your cover changes the spine — that alone is a common cause of rejected uploads.

Full wrap cover dimensions

Your cover is one single image or PDF covering back, spine and front together, with bleed on all four sides:

Width = (trim width × 2) + spine width + 0.25"
Height = trim height + 0.25"

The 0.25" is 0.125" of bleed on each edge. Design anything that touches an edge right out into the bleed, and keep all text at least 0.25" inside the trim line.

Publishing a paperback? Get the KDP specs that actually matter

The margin, bleed, spine and paper rules KDP will reject you for, written out plainly — including the ones their own help pages bury. I’ll email the guide and let you know when the specs change.

Free, and you can leave any time. No spam, ever.

Three mistakes that get covers rejected

The spine is calculated for the wrong paper. White and cream differ by about 10%. On a 300-page book that's nearly a tenth of an inch — plainly visible as a misaligned wrap.
Spine text on a thin book. KDP only prints spine text on books with more than 79 pages. Below that, binding drift of up to 0.0625" would pull your text around onto the front cover. Leave thin spines blank, and in the same colour as the covers so any drift is invisible.
Something sitting in the barcode area. Amazon prints a barcode in a 2" × 1.2" box at the bottom-right of your back cover. Put your blurb there and it will be covered up. The template below marks the exact zone.

Your interior has margin rules too

The gutter — the inside margin against the binding — grows with page count. Get it wrong and your text disappears into the spine:

Page count	Minimum gutter
24 – 150	0.375"
151 – 300	0.500"
301 – 500	0.625"
501 – 700	0.750"
701 – 828	0.875"

Outer, top and bottom margins must be at least 0.25" without bleed, or 0.375" with bleed. Books must be an even number of pages, and at least 24.

Skip the arithmetic entirely

PuzzleBindery builds print-ready puzzle book interiors and their covers together, so the spine width, trim and margins come straight from your live page count. Add a puzzle and the cover resizes itself — the numbers on this page can't go stale, because nothing on your book is typed in twice.

Open the Studio — free

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