The KDP cover calculator works out the full-wrap size of a paperback cover from three inputs: trim size, page count and paper type. The formula is bleed + back cover + spine + front cover + bleed for the width, and bleed + trim height + bleed for the height. Bleed is 0.125 inches (3.2 mm), and spine width is the page count multiplied by the paper’s thickness per page.

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This guide explains the maths behind the calculator so you can check your designer’s file, plan a cover before the interior is final and avoid the usual rejection reasons. It includes worked examples for common trim sizes, a comparison with hardcover and IngramSpark specs, and a pre-upload checklist.

At a glance

• Spine width per page, according to KDP Help: white paper 0.002252 in, cream paper 0.0025 in, standard colour 0.002252 in, premium colour 0.002347 in.
• Paperback bleed is 0.125 in (3.2 mm) on the top, bottom and outside edges. A full-wrap cover adds it on all four outer edges.
• Keep text at least 0.125 in (3.2 mm) inside the trim lines and spine text at least 0.0625 in (1.6 mm) from the spine edges.
• Spine text is only allowed on books of about 80 pages or more. KDP’s help pages give 79 pages as the threshold, and Cover Creator requires 80.
• Upload a single PDF (back, spine and front as one image) at a minimum of 300 DPI.
• Your final page count sets the spine. If the interior changes, recalculate the cover.

What the KDP cover calculator does

KDP’s cover calculator and template generator lets you choose a trim size, paper type, page count and binding, then download a template as a PDF or PNG. The template shows the trim lines, bleed, spine and barcode area for your exact book. Designers place artwork over the template and remove the guide layer before export.

Using the template is always the safest route. Knowing the maths behind it is still worth it, though. You can budget for cover design before your interior is finished, catch a designer working to the wrong page count and see straight away why a cover was rejected.

The cover size formula

KDP Help gives the paperback cover dimensions as:

• Cover width = bleed + back cover width + spine width + front cover width + bleed
• Cover height = bleed + trim height + bleed

Back and front cover widths are each equal to your trim width. Bleed is 0.125 in. So for a 6 x 9 in book, the width is 0.125 + 6 + spine + 6 + 0.125, and the height is 0.125 + 9 + 0.125 = 9.25 in.

Spine width by paper type

Paper / ink	Thickness per page (inches)	Thickness per page (mm)	Spine for 100 pages
Black ink, white paper	0.002252	0.0572	0.2252 in (5.7 mm)
Black ink, cream paper	0.0025	0.0635	0.25 in (6.4 mm)
Standard colour, white paper	0.002252	0.0572	0.2252 in (5.7 mm)
Premium colour, white paper	0.002347	0.0596	0.2347 in (6.0 mm)

Figures are from KDP Help at the time of writing (October 2026). KDP can update specifications, so confirm them in the calculator before you finalise a file. Page count means the full printed page count of your interior PDF, including blank pages and front matter.

Worked examples for common trim sizes

Each example below applies the formula above. Pixel sizes assume 300 DPI. Round your canvas up slightly rather than down, and always check against the template KDP generates for your book.

Book	Spine width	Full cover width	Full cover height	Canvas at 300 DPI
6 x 9 in, 300 pages, white	300 x 0.002252 = 0.6756 in (17.2 mm)	12.9256 in (328.3 mm)	9.25 in (234.9 mm)	about 3,878 x 2,775 px
6 x 9 in, 400 pages, cream	400 x 0.0025 = 1.0 in (25.4 mm)	13.25 in (336.5 mm)	9.25 in (234.9 mm)	about 3,975 x 2,775 px
5 x 8 in, 250 pages, cream	250 x 0.0025 = 0.625 in (15.9 mm)	10.875 in (276.2 mm)	8.25 in (209.5 mm)	about 3,263 x 2,475 px
5.5 x 8.5 in, 120 pages, white	120 x 0.002252 = 0.2702 in (6.9 mm)	11.5202 in (292.6 mm)	8.75 in (222.3 mm)	about 3,456 x 2,625 px
8.5 x 8.5 in, 32 pages, premium colour	32 x 0.002347 = 0.0751 in (1.9 mm)	17.3251 in (440.1 mm)	8.75 in (222.3 mm)	about 5,198 x 2,625 px

Two things stand out. Moving a 6 x 9 novel from white to cream paper adds about 0.25 in of spine per 100 pages, which is enough to throw a cover off if the designer used the wrong paper. And a 32-page picture book has a spine of under 2 mm, so it can’t carry spine text at all. If you are publishing a picture book, the guide to self-publishing a children’s book covers the other print decisions involved.

How to size a KDP paperback cover: step by step

1. Finalise the interior first. Lock trim size, paper type and page count. Any change to the page count changes the spine.
2. Calculate the spine. Multiply the page count by the per-page figure for your paper.
3. Calculate the full size. Width = 0.125 + trim width + spine + trim width + 0.125. Height = trim height + 0.25.
4. Download the KDP template for the same trim, paper and page count, and check your numbers against it.
5. Set up the canvas at the full size, at 300 DPI or higher, in CMYK.
6. Place guides for the trim lines, spine folds, safe zones (0.125 in inside trim) and spine text margin (0.0625 in from each fold).
7. Leave the barcode area clear on the back cover where the template marks it, unless you are supplying your own barcode.
8. Extend background art all the way to the outer bleed edge.
9. Export a single PDF with fonts embedded, transparencies flattened and the template guides removed.
10. Use the online previewer after uploading and order a proof copy before release if you can.

KDP paperback vs hardcover vs IngramSpark: key cover specs

Spec	KDP paperback	KDP hardcover (case laminate)	IngramSpark paperback
Bleed / wrap	0.125 in (3.2 mm) bleed	Image extends 0.51 in (15 mm) past the cover edge, wrapped and glued	0.125 in (3 mm) bleed on all four sides
Text safe zone	At least 0.125 in (3.2 mm) inside trim	At least 0.635 in (16 mm) from the book edge, plus a 0.4 in (10 mm) hinge gap each side of the spine	At least 0.25 in (6 mm) on all sides
Spine text	About 80+ pages; 0.0625 in (1.6 mm) margin	Inside the spine safe area on the template	Not allowed under 48 pages
Barcode	Area marked on the template; KDP can add one	2 x 1.2 in (50.8 x 30.5 mm), lower right of the back cover	Required; 1.75 x 1 in clear area; IngramSpark can add one
Spine width	Page count x per-page paper figure	From the template generator	From IngramSpark’s template generator
File	Single PDF, 300 DPI minimum, CMYK	Single PDF from the hardcover template	PDF (PDF/X-1a recommended), 300 ppi, CMYK

Because paper stocks differ, a cover built for KDP won’t fit IngramSpark exactly, even at the same trim size and page count. Generate a separate template for each platform. The KDP vs IngramSpark comparison explains when it makes sense to use both.

Book spine design tips

• Centre spine text on the spine’s centre line, not by eye. A shift during trimming is noticeable on thin spines.
• Avoid hard lines at the fold. KDP allows some variance either side of the fold lines, so a colour change exactly on the fold can wrap visibly onto the front or back. Let background colours run across the spine.
• Keep it readable. Title and author name in a weight that reads from a shelf. KDP sets a 7-point minimum text size for covers.
• Match orientation to your market. English-language books usually run spine text top to bottom. If you follow a different convention, keep it consistent across a series.
• Think series. Spines that line up visually on a shelf help readers spot the next book. See planning a book series for more on series consistency.

Common mistakes that get covers rejected

• Wrong page count. The cover was built for a draft interior and the final PDF has a different number of pages.
• Wrong paper type. Cream and white give different spine widths.
• No bleed. Background art stops at the trim line, leaving white slivers after trimming.
• Text in the danger zone. Titles, author names or back-cover text sit too close to the trim or fold lines.
• Spine text on a thin book. Books under about 80 pages can’t carry spine text.
• Template guides left visible. The template’s coloured guide layer must be hidden before export.
• Low resolution or RGB. Images under 300 DPI print blurry. Convert to CMYK for print.
• Separate front and back files. KDP needs a single PDF containing back, spine and front.
• Barcode overlap. Back-cover text or images run into the barcode area.

Most of these problems come from a mismatch between the brief and the final interior. When you commission a designer, give them the final trim, paper and page count in writing. The guide to choosing a book cover designer covers what to include in a brief. For the bigger picture on print editions, see adding a print-on-demand paperback.

Pre-upload cover checklist

• Interior PDF is final, and its page count matches the number used for the cover.
• Paper type matches (white, cream, standard or premium colour).
• Width and height match the KDP template to within a fraction of a millimetre.
• Background extends to the outer bleed edge on all sides.
• All text is at least 0.125 in inside trim, and spine text is at least 0.0625 in from each fold.
• Barcode area is clear, or your own barcode is the correct size and placement.
• Images are at 300 DPI or higher, CMYK, flattened, with fonts embedded.
• Template guides are removed.
• File is a single PDF, ideally 40 MB or less as KDP recommends.
• Proof copy ordered before you announce a release date, if your timeline allows.

Related guide: Book Sizes: How to Choose the Right Trim Without Regret.

Related guide: How to Publish a Coloring Book Without Costly Mistakes.

Sources this guide draws on: Amazon KDP Help on creating a paperback cover and the cover calculator and template generator, Amazon KDP Help on hardcover cover specifications, and IngramSpark Help on cover file creation. Figures were checked in October 2026 and may change.

Frequently asked questions

How do I calculate spine width for KDP?

Multiply your interior page count by the per-page thickness for your paper type. That is 0.002252 in for white or standard colour, 0.0025 in for cream, and 0.002347 in for premium colour. For example, 300 pages on white paper gives a 0.6756 in spine.

What size should my KDP paperback cover be?

Width is 0.125 in bleed + trim width + spine width + trim width + 0.125 in bleed. Height is trim height + 0.25 in. A 6 x 9 in book with 300 white pages is about 12.93 x 9.25 in.

Can I put text on the spine of a thin book?

Not on KDP if the book is under roughly 80 pages. KDP’s help pages give 79 pages as the threshold, and Cover Creator requires 80. IngramSpark doesn’t allow spine text on paperbacks under 48 pages.

Does KDP add a barcode for me?

Yes. If you don’t include one, KDP places a barcode on the back cover. The template shows where it goes, so keep that area clear of important text and images.

Can I use the same cover file for KDP and IngramSpark?

Usually not without changes. The platforms use different paper stocks and specifications, so spine widths can differ. Generate a template on each platform and adjust the file to match.

Once you know where each number comes from, cover sizing is a short calculation. Lock the interior, run the numbers, check them against KDP’s template and order a proof. That way your cover goes through review first time.