KDP Spine Width Calculator

Spine width depends on your page count and paper. Enter them to see the spine in inches, millimetres and pixels, next to the full cover size. For a paperback, the spine figure is the one KDP's cover calculator gives.

Your book

Check your finished cover

Drop your cover PDF hereOr click to choose it. Your file stays on this device.

Waiting for a cover

Page size–
One page–
Text inside safe area–
Spine text–
Barcode area–
Image resolution–
Fonts embedded–
Artwork near trim–

Colour and transparency aren't checked yet, and text that's part of an image can only be checked near the trim.

Full cover width

12.700in

322.6 mm · 3,810 px

Full cover height

9.250in

234.9 mm · 2,775 px

Spine width

0.450in

11.4 mm · 135 px

Spine text

Allowed

80 pages or more

Your cover, to scale

Example artwork. Pixels are at 300 DPI.

A coastal town. A missing boat.

When the sea gives back what it took, one family must decide what the truth is worth.

The Long Tide

Mira Calloway

Barcode

Bleed: Extra artwork past the cut. It gets trimmed away.
Trim: Where the printed book is cut.
Safe area: Keep words and logos inside this line.
Spine: Its width depends on your page count.

How KDP spine width is calculated

The spine is the strip between the back and front covers, and it has to match the thickness of your printed pages. KDP's figure for a paperback is the page count multiplied by a thickness per page, which depends on the paper.

For a 200-page paperback on white paper, that is 200 x 0.002252 = 0.450 in. On cream paper the same book has a spine of 0.500 in. The difference is small, but a spine that is wrong by a fraction of a millimetre can move text across a fold.

A hardcover adds a fixed 0.189 in to the same sum, so its spine is pages x paper + 0.189 in. Choose Hardcover in the calculator above, or see the hardcover calculator.

Spine thickness per page

Multiply your page count by the figure for your paper. Inches per page.

Interior	Per page
Black ink, white paper	0.002252
Black ink, cream paper	0.0025
Black ink, groundwood paper	0.00235
Standard colour, white paper	0.002252
Premium colour, white paper	0.002347

Spine width by page count

A quick reference for a 6 x 9 paperback, in inches. Trim size doesn't change the spine, but every page you add or remove does. The calculator above gives your exact figure.

Pages	Black, white	Black, cream	Black, groundwood	Standard colour	Premium colour
100	0.225	0.250	0.235	0.225	0.235
200	0.450	0.500	0.470	0.450	0.469
300	0.676	0.750	0.705	0.676	0.704
400	0.901	1.000	0.940	0.901	0.939
500	1.126	1.250	1.175	1.126	1.173

Use your final page count

Every extra page changes the spine, which changes the width of the whole cover and moves the front cover to the right. If you add a chapter, a page of ads or a blank page after the cover is designed, rebuild the cover on a fresh template instead of stretching the old one.

KDP rounds an odd page count up to an even number when it prints the book. Amazon's calculator takes the number as you type it, and so does this tool, so an odd count is shown as typed. The difference is under 0.003 in, but entering the even number you will actually print keeps the figures in step with KDP's.

Paper limits apply too. Most trim sizes take up to the page counts below, and 8.5 x 8.5 and 8.5 x 11 books have a lower maximum for some papers. The minimum is 24 pages, or 72 for standard colour. Above the maximum for a listed trim size, the calculator says so instead of giving a spine. KDP lists no maximum for custom sizes, so there it only shows a note.

Maximum pages by paper

From Amazon's print options. The second column applies to 8.5 x 8.5 and 8.5 x 11 trims.

Interior	Most trims	8.5 x 8.5 and 8.5 x 11
Black ink, white paper	828	590
Black ink, cream paper	776	550
Black ink, groundwood paper	812	578
Standard colour, white paper	600	600
Premium colour, white paper	828	590

Putting text on the spine

A narrow spine can't hold a title. KDP's guidance on the minimum page count for spine text is inconsistent, so the calculator treats 80 pages or more as safe, and warns at exactly 79.

When you do add spine text, keep it at least 0.0625 in from each edge of the spine. The printed fold can vary by 0.0625 in either side, so text near the edge can wrap onto the front or back cover. Anything you need people to read should also be 7 point or larger.

The checker looks at the spine of your finished PDF and flags text that runs close to a fold. Add your PDF above, with the same page count and paper as the book you will print, and check the spine row of the result. Your file is read on your device and never uploaded.

These figures are measurements, not a promise that KDP will accept a file. KDP reviews your files after you submit them, so always look at your cover in its print previewer. For the full cover size and margins, see the main calculator.

More KDP cover guides

The same free tool, set up for other questions. Your files stay on your device.