If you are getting ready to upload a paperback to Amazon KDP, the cover file is where most first-time authors trip up. The interior is forgiving; the cover is not. One wrong number and the upload fails or, worse, the printed book comes back with the spine text sliding onto the front cover. This guide gives you the exact formula, a table of full cover sizes for the most common trim sizes, and a worked example you can copy.
If you would rather skip the arithmetic, our free KDP Spine Width & Cover Size Calculator does all of this for you and gives you a downloadable 300 DPI template. Everything below is the reasoning behind it, so you can check the numbers yourself.
The one formula that matters
According to KDP’s own Help page on paperback cover dimensions, your full cover (front, spine and back laid flat as a single image) is built like this:
- Cover width = bleed + back cover width + spine width + front cover width + bleed
- Cover height = bleed + trim height + bleed
Bleed is 0.125″ (3.2 mm) added to the top, bottom and outside edges. Because you add it on both sides of the width, that is 0.25″ extra in total, both across and up-and-down. Back cover width and front cover width each equal your trim width.
So, written out in plain numbers: full cover width = (2 × trim width) + spine width + 0.25″, and full cover height = trim height + 0.25″.
Step one: work out your spine width
The spine depends on two things you control: your page count and your paper. KDP publishes a per-page multiplier for each paper type:
| Paper / ink | Spine width per page |
|---|---|
| Black ink, white paper | 0.002252″ |
| Black ink, cream paper | 0.0025″ |
| Standard color ink | 0.002252″ |
| Premium color ink | 0.002347″ |
Multiply your final page count by the matching number. A 300-page book on white paper has a spine of 300 × 0.002252 = 0.6756″. On cream paper the same book is 300 × 0.0025 = 0.75″. That difference of about 0.07″ sounds tiny, but it is enough to misalign wrap-around artwork, which is why choosing your paper before you design the cover matters.
Use your final page count, including blank pages at the front and back. If you add or remove even a few pages after the cover is done, recalculate the spine.
Full cover sizes for common trim sizes (300 pages)
Here are the calculated full cover dimensions for five popular trim sizes at 300 pages. These are worked from the formula above, so you can reproduce every figure with a calculator. Sizes are in inches: width × height.
| Trim size | Spine (white) | Full cover, white | Spine (cream) | Full cover, cream |
|---|---|---|---|---|
| 5″ × 8″ | 0.6756″ | 10.9256″ × 8.25″ | 0.75″ | 11.0″ × 8.25″ |
| 5.25″ × 8″ | 0.6756″ | 11.4256″ × 8.25″ | 0.75″ | 11.5″ × 8.25″ |
| 5.5″ × 8.5″ | 0.6756″ | 11.9256″ × 8.75″ | 0.75″ | 12.0″ × 8.75″ |
| 6″ × 9″ | 0.6756″ | 12.9256″ × 9.25″ | 0.75″ | 13.0″ × 9.25″ |
| 8.5″ × 11″ | 0.6756″ | 17.9256″ × 11.25″ | 0.75″ | 18.0″ × 11.25″ |
Notice how the height never changes with page count, only with trim height. Page count only moves the width, through the spine. For other trim sizes or page counts, plug your numbers into the free spine and cover size calculator. Not sure which trim size to pick in the first place? Think about your genre, how your competitors look on the shelf, and what your printing cost will be before you commit.
A worked example, start to finish
Say you are publishing a 6″ × 9″ novel with 240 pages on cream paper.
- Spine: 240 × 0.0025″ = 0.60″.
- Width: (2 × 6) + 0.60 + 0.25 = 12.85″.
- Height: 9 + 0.25 = 9.25″.
- Final canvas: 12.85″ × 9.25″.
To build the file in a design tool at 300 DPI, multiply each dimension by 300: that is 3,855 × 2,775 pixels. Place a vertical guide at 0.125″ plus the back cover width (6″) from the left edge, and another 0.60″ further right. The area between the two guides is your spine; the area to the right of it is the front cover.
Bleed, safe zone and spine text
Three margins keep your artwork from being trimmed into trouble. Per the same KDP Help page:
- Bleed (0.125″ / 3.2 mm): extend backgrounds and images all the way to the outer edge of the cover file on the top, bottom and outside edges. If your color stops at the trim line, a thin white sliver can show after cutting.
- Text margin (at least 0.125″ / 3.2 mm inside the trim lines): keep front and back cover text away from the edges so it is not clipped.
- Spine text clearance (at least 0.0625″ / 1.6 mm): leave at least this much space between spine text and the edge of the spine.
KDP also says a book needs at least 79 pages before you can include spine text. Below that, the spine is simply too thin. At 79 pages on white paper the spine is only about 0.18″, so a short book is usually better off with a clean, text-free spine. You can also upload your cover with or without a barcode; if you leave it off, KDP places one on the back cover for you, so keep that area of the back cover uncluttered.
Common mistakes that cause rejected uploads
- Using a page count from an early draft. Recalculate after your last formatting change.
- Forgetting bleed on the outside edges. Both the width and the height need the extra 0.125″ on each outer side.
- Picking the wrong paper multiplier. Cream and white are not interchangeable in the formula.
- Putting key text too close to the trim or the spine fold. Design as if the edges could shift slightly, because in print they can.
- Designing the front cover first, the spine last. Work out the full canvas first, then design inside it.
Before you upload, open your PDF and confirm its pixel or inch dimensions match the canvas you calculated. KDP’s Cover Creator and previewer are useful as a final check, but the numbers should already be right before you get there.
Your cover is one piece of the launch
A correctly sized cover file gets your book printed; it does not get your book noticed. Once the files are done, you will need an author bio for the book page and the back cover (our author bio guide with examples and the free Author Bio Generator help here), and a plan for the weeks around release, which our book launch checklist walks through. If you want everything you send to reviewers, podcasters and bloggers in one tidy package, the Author Media Kit template is built for exactly that.
Quick reference
- Full width = (2 × trim width) + spine + 0.25″
- Full height = trim height + 0.25″
- Spine = pages × 0.002252″ (white, standard color), × 0.0025″ (cream), × 0.002347″ (premium color)
- Spine text only at 79+ pages, with 0.0625″ clearance
- Keep text at least 0.125″ inside the trim
Rather than doing this by hand every time you change a page count, use the KDP Spine Width & Cover Size Calculator and download the template. These figures come from KDP’s official Help pages; KDP can update its specifications, so always double-check against the current KDP Help page before you upload a final file.
Not sure which size to choose in the first place? Read KDP trim sizes explained for how standard, large and custom sizes compare.
Only have a word count so far? The free Word Count to Page Count Calculator estimates your paperback page count, which is the number you need before the cover dimensions above can be finalised.
Designing in Canva? Follow our step-by-step guide to making a KDP paperback cover in Canva with a free template.
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