KDP spine width and cover size calculator, paperback and hardcover

How it works

The spine is your page count times the thickness of a page: 0.0025 in on cream paper and 0.002252 in on white, in black ink. A hardcover's spine adds 0.189 in (4.8 mm) for its case.

A paperback cover is one image: back, spine and front side by side, with 0.125 in of bleed on the top, bottom and outside edges. So its width is 0.125 + trim width + spine + trim width + 0.125 in, and its height is the trim height plus 0.25 in.

A hardcover's case wraps boards that are 5 mm wider and 6 mm taller than the trim, with 15 mm of wrap turned in on every edge, so its cover is larger than a paperback's of the same trim.

KDP prints text on the spine only from 79 pages: the calculator tells you whether your book has room.

A worked example

A 6 × 9 in paperback of 300 pages on cream paper has a spine of 300 × 0.0025 = 0.75 in. Its full cover is 0.125 + 6 + 0.75 + 6 + 0.125 = 13.0 in wide and 9 + 0.25 = 9.25 in tall.

The same book as a hardcover has a 0.939 in spine and a case cover of about 14.51 × 10.42 in.

Questions authors ask

Why does cream paper make a thicker spine?

Cream paper is a little thicker than white: 300 pages come to 0.75 in on cream and about 0.68 in on white. Choose the paper before you design the spine.

Which page counts can KDP print?

Paperbacks from 24 pages up to 776 on cream paper or 828 on white, and hardcovers from 75 to 550 pages.

Do blank pages count?

Yes. Count every page of the interior file, blank ones included: that's what KDP prints and binds.

Where does the barcode go?

KDP keeps an area low on the back cover, by the spine, for the ISBN barcode, and prints one there itself if your cover has none. Keep text and important artwork out of it.

Will the size change if I add pages?

Yes: every page widens the spine. Work out the cover from the final interior, after the last edit.

Sources

Checked on 17 October 2026 against KDP: Create a paperback cover, KDP: Create a hardcover cover, KDP: Print options (trims and page counts). Stores change their rules: their own pages have the final word.