Cover & Spine Calculator

Spine width, full cover size and pixel dimensions for every KDP trim size.

Free · No sign-up · Runs in your browser · Rules checked 2026-10-15

Cover size

How the cover size is worked out

Spine width is the page count multiplied by the per-page thickness KDP publishes for the paper you choose. The full wrap cover is the back cover, the spine and the front cover side by side, plus a 0.125 inch bleed on all outer edges.

Pixel sizes are shown at 300 dpi. Keep important text at least 0.25 inch inside the trim edge, and leave the spine blank for books too thin for spine text. Always load your finished cover into KDP's previewer; it is the final judge.

Frequently asked questions

How is spine width worked out?

Page count multiplied by the paper thickness KDP publishes for the paper and ink type you pick. The result is shown in inches and millimetres.

Does the spine text rule matter?

KDP does not allow spine text on very thin books, and it publishes a minimum page count for it. The tool warns you when your page count is too low.

Should I use the numbers or KDP's own template?

Use whichever you like, and always check the final cover in KDP's previewer. The numbers here follow KDP's published formulas for planning your design.