What bleed does KDP require on paperback covers?

KDP requires 0.125 inches (3.2mm) of bleed on the top, bottom, and outside edges of your cover file. Bleed is added to the trim height (top and bottom) and to the outside edges of the front and back cover width, not to the spine itself.

Is this spine width formula verified against Amazon's own numbers?

Yes. This calculator uses the exact coefficients published on Amazon KDP's official Create a Paperback Cover help page, and the output is cross-checked against KDP's own worked example: a 200-page white paper book produces a 0.450 inch spine (200 x 0.002252 = 0.4504, which rounds to 0.450).

KDP Spine Width Calculator (2026)

Q: What is the formula for KDP spine width?

Amazon KDP's published formula is: spine width = page count x per-page thickness. The per-page thickness is 0.002252 inches for white paper, 0.0025 inches for cream paper, and 0.002347 inches for premium color paper. There is no separate fixed base amount added — it is a straight multiplication of page count by the paper coefficient, per KDP's own Create a Paperback Cover help page.

Q: How many pages do I need for spine text?

KDP only prints text on the spine if your book has at least 79 pages. Below that, the spine is too narrow to reliably hold readable text, and KDP will reject a cover file that includes spine text on a shorter book.

Q: Does trim size affect spine width?

No. Spine width depends only on page count and paper type, not on trim size. Trim size affects the front and back cover panel width, which is added on either side of the spine when calculating your full cover width.

Page Count

Paper Type

Trim Size

Spine width

Spine width (mm)

Full cover width (with bleed)

Full cover height (with bleed)

Full cover size @ 300 DPI

Spine text eligible?

Recommended inside gutter

How KDP Calculates Spine Width

Amazon KDP's published formula (from its official "Create a Paperback Cover" help page) is a straight multiplication of page count by a per-page thickness coefficient — there is no separate fixed base width added on top:

Spine Width = Page Count × Per-Page Thickness

The per-page thickness depends on your paper and ink choice:

Paper / Ink	Per-Page Thickness
White paper (black ink or standard color)	0.002252" (0.0572mm)
Cream paper (black ink only)	0.0025" (0.0635mm)
Premium color paper	0.002347" (0.0596mm)

Verified example (straight from Amazon's own help documentation): a 200-page white paper book has a spine width of 200 × 0.002252 = 0.4504", which KDP publishes as 0.450". This calculator uses the identical coefficients, so it will reproduce that number exactly.

Full Cover Size With Bleed

Your total cover file — the single flat PDF that includes back cover, spine, and front cover — needs bleed added on the outside edges before it goes to KDP:

Cover Width = Bleed + Back Cover Width + Spine Width + Front Cover Width + Bleed
Cover Height = Bleed + Trim Height + Bleed

KDP's bleed requirement is 0.125" (3.2mm) per edge. Bleed is added to the top, bottom, and outside edges of the front/back cover panels — it is not added to the spine itself, since the spine doesn't get trimmed.

Interior Page Margins & Gutter

The "gutter" is the extra inside margin every interior page needs so text isn't lost in the fold once the book is bound. KDP's recommended inside margin scales with page count — thicker books need a wider gutter:

Page Count	Recommended Inside Gutter
24–150 pages	0.375" (9.5mm)
151–300 pages	0.500" (12.7mm)
301–500 pages	0.625" (15.9mm)
500+ pages	0.750" (19.1mm)

Outside, top, and bottom margins should be at least 0.250" (0.375" if your design bleeds off the page edge). Also leave a clear 2.0" × 1.2" zone in the lower right corner of the back cover — KDP stamps its own distribution barcode there and will reject files that have art or text underneath it.

Minimum Pages for Spine Text

KDP will only print text on the spine if your book has at least 79 pages (Cover Creator requires 80). Below that threshold, the spine is considered too narrow for legible text, and a cover file with spine text on a shorter book will be rejected during review. If your low-content book runs under 79 pages, leave the spine blank.

Frequently Asked Questions

What is the formula for KDP spine width?

Spine width = page count × per-page thickness. The coefficient is 0.002252" for white paper, 0.0025" for cream paper, and 0.002347" for premium color paper — straight from Amazon KDP's own Create a Paperback Cover documentation, with no separate fixed base added.

How many pages do I need for spine text?

At least 79 pages (80 if you're using KDP's Cover Creator tool). Shorter books should leave the spine blank — a cover with spine text under that threshold will be rejected.

Does trim size affect spine width?

No. Spine width is driven only by page count and paper type. Trim size determines the width of the front and back cover panels on either side of the spine, which matters for your full cover width but not for the spine measurement itself.

What bleed does KDP require?

0.125" (3.2mm) on the top, bottom, and outside edges of the cover file. This is added when calculating full cover width and height, but not against the spine.

Is this verified against Amazon's own numbers?

Yes — the coefficients used here are copied directly from Amazon KDP's official help documentation (kdp.amazon.com, "Create a Paperback Cover"), and the output matches KDP's own published example of a 200-page white-paper book producing a 0.450" spine.

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