A KDP paperback cover is one PDF containing the back cover, spine and front cover, with 0.125 in of bleed on the outside edges. The spine width is your page count multiplied by a paper factor (0.002252 in per page for white paper, 0.0025 in for cream), spine text is only allowed above KDP’s minimum page count, and the barcode needs a clear space on the back cover. ProofSlip, a Windows app from Automata Labs, checks a cover PDF against a paperback cover preset, boxes problems such as spine text, the barcode area, small text and low-resolution images on the page, and exports a report, all on your PC.
This guide gives KDP’s numbers as published on its help pages on 20 October 2026, a worked example, and a pre-upload check.
Check the cover PDF against the job before KDP does, and see each problem boxed on the page.
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How does KDP calculate spine width?
KDP’s Create a Paperback Cover page gives the spine as page count multiplied by a factor for the paper:
| Ink and paper | Spine width per page |
|---|---|
| Black and white, white paper | 0.002252 in (0.0572 mm) |
| Black and white, cream paper | 0.0025 in (0.0635 mm) |
| Premium color paper | 0.002347 in (0.0596 mm) |
| Standard color paper | 0.002252 in (0.0572 mm) |
KDP’s Paperback Submission Guidelines add groundwood paper at 0.00235 in per page. KDP calculates your page count from the manuscript and rounds up to an even number if necessary, so use KDP’s count, not the last page number in your file.
The full cover size then follows:
- Cover width = bleed + back cover width + spine width + front cover width + bleed
- Cover height = bleed + trim height + bleed
Bleed is 0.125 in (3.2 mm) on the top, bottom and outside edges.
What does a worked example look like?
A 6 x 9 in paperback with 300 pages:
| Paper | Spine | Cover width | Cover height |
|---|---|---|---|
| White | 300 x 0.002252 = 0.6756 in | 0.125 + 6 + 0.6756 + 6 + 0.125 = 12.9256 in | 0.125 + 9 + 0.125 = 9.25 in |
| Cream | 300 x 0.0025 = 0.75 in | 13.0 in | 9.25 in |
| Premium color | 300 x 0.002347 = 0.7041 in | 12.9541 in | 9.25 in |
Switching from white to cream paper after the cover is designed changes the spine by about 0.07 in at 300 pages, which is enough to push spine text off center. Recalculate whenever the page count or paper changes. KDP’s cover calculator and template generator does the same arithmetic and draws the layout.
How many pages do you need for spine text?
KDP’s wording is not fully consistent. The Create a Paperback Cover page says a book “must have at least 79 pages” to include spine text and that covers with spine text under 79 pages will be rejected, while the spine text section on the same page and the submission guidelines say KDP only prints spine text “on books with more than 79 pages.” If you use Cover Creator, the minimum is 80 pages.
The practical answer: if your book is right at 79 or 80 pages, check the cover calculator for your exact settings before adding spine text. The bigger issue is space. KDP asks for at least 0.0625 in (1.6 mm) between spine text and the edge of the spine, and allows 0.0625 in of variance on either side of the fold lines. On a 79-page book on white paper the spine is about 0.178 in wide, which leaves roughly 0.05 in for the text after both margins. Thin books often look better with no spine text at all.
Where does the barcode go?
KDP’s Barcodes page gives you three options: use Cover Creator, upload a cover without a barcode and let KDP add one, or upload a cover with your own barcode.
| If you | KDP’s rule |
|---|---|
| Leave the barcode off | KDP adds one to the back cover. Covers with images or text in the barcode location are rejected |
| Supply your own | Suggested size 2 x 1.2 in (minimum 1.4 x 0.8 in), at least 0.25 in from the spine and trim, 100% black on a solid white background, right side up and square, not flattened into the cover image |
| Use a raster barcode | 300 PPI; vector is preferred |
| Include an ISBN in the barcode | It must be valid and match your book’s ISBN exactly |
KDP recommends the Amazon-placed barcode if your own fails validation. Either way, keep the lower part of the back cover near the spine clear of important text and art. You can add a QR code, but not in the space reserved for the ISBN barcode.
See spine text, the barcode area and small text boxed on the cover before you upload.
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What other cover rules cause rejections?
From KDP’s cover page and submission guidelines:
| Rule | KDP’s requirement |
|---|---|
| File | A single PDF with back, spine and front as one image; covers over 650 MB will not convert, 40 MB or less recommended |
| Text position | At least 0.125 in inside the trim lines; no front or back text running into the spine |
| Text size | At least 7 point |
| Images | 300 DPI minimum, CMYK recommended |
| Transparency | Flatten all transparencies |
| Fonts | Embed fonts |
| Marks | Remove crop marks, color bars and template text |
| Security | Remove file security; locked or encrypted files fail review |
| Color | No spot colors; KDP recommends converting them to CMYK, and does not recommend multiple color spaces or embedded color profiles |
| Book details | Cover text must match the title, author and ISBN entered at setup |
Our guides on checking that fonts are embedded and checking bleed and trim boxes cover two of these in depth, and the KDP paperback PDF check covers the interior file.
How do you check a cover with ProofSlip?
ProofSlip checks print PDFs, EPUBs and Word manuscripts on your PC and says in plain language what to fix:
- Pick the paperback cover preset. The verdict means “fits this job”: size, bleed, spine, safe area and colour are judged against the preset.
- Drop the cover PDF on the window. ProofSlip checks fonts, image resolution, colour spaces and the plates the file needs; text near the trim, spine text and the barcode area; and small text, rich black, hairlines, ink limit, white overprint, transparency and printable comments.
- Select a finding. Its page opens with the problem boxed and the trim and safe area drawn in.
- Check the book details. ProofSlip validates ISBN check digits in your book details, so a mistyped ISBN is caught before you build the barcode from it. Our guide to the ISBN check digit explains the arithmetic.
- Export the report. The HTML report shows the findings with your name and logo, which helps when a designer or client needs to see what changed.
Before the check, compare the cover PDF’s page size, shown in your PDF viewer’s document properties, with your own calculation from the table above. If they differ, the page count or paper in your template is out of date. Drop the interior PDF, the EPUB and the Word manuscript in the same run to check the whole book at once. Files never leave the PC and are never changed.
Frequently asked questions
How wide is the spine for a 200-page book?
On white paper, 200 x 0.002252 = 0.4504 in. On cream paper, 200 x 0.0025 = 0.5 in.
Does KDP add the barcode for me?
Yes. If you upload a cover without a barcode, KDP places one on the back cover. Keep that area clear of important text and images.
What is the minimum font size on a KDP cover?
KDP asks for text of at least 7 point.
Can I keep RGB images in my cover?
KDP says images should be in CMYK to make sure the cover looks good in print, and does not recommend mixing color spaces in one file.
Does ProofSlip upload my cover?
No. ProofSlip has no account and no upload. Files never leave your PC and are never changed.
Try ProofSlip
ProofSlip is a one-time purchase in the Microsoft Store with a free trial. Check your current cover PDF and your interior in one run before your next upload. More detail is on the ProofSlip product page.
Check covers, interiors, EPUBs and manuscripts on your PC before you send them.
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Kindle Direct Publishing and KDP are trademarks of Amazon.com, Inc. or its affiliates. ProofSlip is not affiliated with Amazon.
Last updated 20 October 2026. Published by Automata Labs, a software company in Canada.