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Cover design guide

Book cover spine size: page count and paper decide it.

Spine width is calculated, not guessed. Get the number right and the wrap fits the book block.

Checked:

Page count times paper factorAdd 0.125-inch bleed all aroundOne continuous wrap PDF

Paperback cover dimensions

Spine width0.450 in11.44 mm
Full cover size12.700 × 9.250 in322.59 × 234.95 mm
Canvas (300 DPI · Canva)3810 × 2775 px300 DPI · Canva custom size
Spine text

Eligible: more than 79 pages. Keep at least 0.0625 in from each spine edge.

Paperback calculation uses KDP's published 0.125 in bleed and current paper thickness factors. Always confirm the final page count after interior formatting.

The formula behind the spine

KDP computes the spine as final page count times a paper factor: 0.002252 for white, 0.0025 for cream, 0.002347 for premium color.

  • Use the final page count, never the draft
  • Recalculate after every layout change
  • No spine text below 80 pages

Generating the full wrap

Enter page count, trim size, and paper into the cover calculator. It returns the full wrap with bleed and an SVG guide for your design file.

Next release checks

Free KDP cover size calculator

Recalculate the full wrap when KDP flags your cover size.

A cover that looked fine in the preview can still be sized from the wrong page count. Rebuild the spine, bleed, and wrap from your final page count, trim, and paper type before you place cover art.Open check

Publishing glossary

Spine width: how thick your paperback will be.

Spine width is the cover's spine panel thickness, calculated from page count and paper type.Open check

KDP trim size recommender

Choose a KDP book size before margins and cover geometry.

Start from reading experience and content type, not the default in a design app. Then check whether the expected page count still feels practical.Open check

FAQ

Frequently asked questions

How do I know my final page count?

Format the interior first. The formatted PDF's page count is the number the spine formula uses.

What happens if the spine is 1mm off?

The cover shifts against the block. KDP rejects files where the spine width does not match the computed value.

Do all paperbacks need spine text?

No — but if you add it, it must be placed correctly. KDP recommends spine text only on books with enough width (usually 79+ pages), and it must be centered between trim lines and never touch the fold. Books that are too thin should use a clean spine with no text, which is a common professional choice.

Get the exact wrap dimensions.

Calculate the full cover with spine and bleed in seconds, free.

Open the cover calculator