Free calculatorKDP cover sizeSpine · bleed · full wrap

KDP cover calculator

Enter your trim size, final page count, and paper. Get the exact spine width, full-wrap dimensions, and spine-text rules for a print-ready paperback cover — with the dated Amazon formula shown.

Editorially reviewed by David Weaver, BookWriter founder and bestselling author since 2008 · Updated July 17, 2026

Direct answer

What size should a KDP cover be?

A full-wrap KDP cover depends on five things: trim width, trim height, final page count, paper type, and bleed. Spine width is your page count times a per-paper thickness; the full canvas adds both trim widths, the spine, and 0.125-inch bleed on every outside edge. Use your final page count, never an estimate.

Free calculator

KDP full-wrap cover calculator

Every dimension you need for a print-ready paperback wrap — spine, bleed, and total canvas.

Spine width0.45″ · 11.4 mm · 135 px @ 300dpi
Full cover width12.7″ · 322.6 mm · 3810 px @ 300dpi
Full cover height9.25″ · 234.9 mm · 2775 px @ 300dpi

Spine text allowed. Keep it inside a safe width of 0.325″.

Spine multiplier 0.002252″/page · bleed 0.125″/edge · from Amazon KDP cover specifications, verified July 17, 2026. This is a close planning estimate; KDP’s own cover calculator and template is the authority. Page count drives spine width, so use your final rendered count and confirm against the current specification before you print.

Why the number matters

The two mistakes behind almost every rejected cover

A print cover is not a picture — it is a piece of manufacturing with exact tolerances. Get the front looking beautiful and the spine width wrong, and the whole wrap is rejected or, worse, prints with the title bleeding onto the front. The math is not hard, but it is unforgiving, and almost every rejected cover comes down to the same two mistakes.

The anatomy of a full-wrap cover

A paperback cover is one flat canvas that wraps the whole book: the back cover on the left, the spine in the middle, and the front cover on the right, with a margin of bleed around the outside that gets trimmed off. That is why you cannot design a KDP cover at "6 by 9" — that is the trim size of one face. The file you upload is more than twice as wide, and the exact width depends on how thick the book is.

The thickness is the spine, and the spine is the part people get wrong, because it is the only dimension you cannot read off a ruler. It is computed: your final page count times a per-page paper thickness that KDP publishes. Thicker paper, or more pages, means a wider spine, which means a wider total canvas — so a cover built for one page count simply does not fit a different one.

Page count is not a detail — it is the spine

Here is the mistake that rejects more covers than any other: designing the wrap from an estimated page count. You think the book is 200 pages, you build a cover, then the formatted interior comes back at 232 pages and the spine you designed for is now too narrow. Because spine width is page count times a fixed multiplier, the error is mechanical and certain — not a matter of taste.

StagePage countSpine widthFull cover width (6×9, white)
Early estimate200≈ 0.450″≈ 12.700″
Final rendered232≈ 0.523″≈ 12.772″

White paper at 0.002252″/page; full width = 2 × 6″ + spine + 0.25″ bleed. A 72-thousandths-of-an-inch shift is enough to reject a submitted cover.

Design the cover last, from the page count of the interior you are actually going to print. If the interior changes, the cover is no longer valid — recalculate.

Bleed, safe areas, and spine text

Two safety margins keep a cover printable. Bleed is the 0.125 inches of artwork that extends past every outside trim edge, so that natural variation in the cutting never leaves a white edge — anything important must sit inside the trim, not in the bleed. The spine has its own safe area: even when your book is thick enough for spine text (KDP allows it at 79 pages and up), keep that text about 0.0625 inches clear of each fold, because binding shifts slightly and text pressed to the fold gets clipped.

None of these numbers are yours to invent — they come from KDP, and KDP updates its specifications. That is why the calculator shows the exact multiplier and bleed it used and the date they were verified, and links the source. Treat the output as an accurate working figure, then confirm against the current KDP specification the day you upload.

Definition

A full-wrap cover — one flat print canvas covering the back, spine, and front of a paperback at once, sized from the trim dimensions, the final page count (which sets the spine), the paper thickness, and 0.125-inch bleed on every outside edge.

Product previewAvailability

This calculator is fully live and free. The connected Cover Studio that carries an approved cover direction into BookWriter’s production handoff is a Product preview — available as a private developer-mode connection, not a public app-directory listing.

Connect BookWriter to ChatGPT through a private developer-mode app: in ChatGPT on the web, open Settings → Apps → Advanced Settings and enable Developer mode. Then open Apps, choose Create, paste the BookWriter MCP server URL, authorize with your BookWriter account, and scan the tools. Full connected write actions currently require an eligible ChatGPT Business, Enterprise, or Edu workspace.

See the current setup guide →

Get the page count right before you size the spine

Write and finish your interior in BookWriter so your final page count is real — then the spine width and cover size you calculate here are the ones you actually print.

Your included Connect book is free, with no BookWriter credit card. Connected Cover Studio is a Product preview.

Start your included Connect bookDesign the cover concept first

Frequently asked questions

Sources

Verified on July 17, 2026

Platform specifications, policies, and product behavior change. Each source is dated above; verify against the primary source before relying on it for a print run or submission.

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