Publishing a book on KDP requires very strict rules. When you upload a Kindle ebook cover, use a single image built at a 1.6 to 1 ratio. Make sure to maintain the standard image size of 1600 pixels wide by 2560 pixels tall. Paperback covers don’t have a fixed size, and if anyone claims about this publishing, they have never published a real book.
You can easily avoid this mistake by getting your KDP book cover size using the official cover calculator tools. The tools instantly build a custom template; download this and build your artwork directly over it. Follow the rest of this guide to get every technical detail before landing your final project.
Why the 1.6 to 1 ratio keeps showing up
The aspect ratio is usually the first thing that gets rejected. If you try to upload a square image, it gets cropped, and a wide image gets bars on the sides. A file that is 1,600 pixels wide by 2,560 pixels tall sits just above the minimum line, which is why you see that specific size everywhere.
Keep the important elements dead center. Store thumbnails crop aggressively from the edges, and the edges are exactly where most people decide to put their subtitle. It happens every time. It is the single most common fix on a cover that looks perfect on your monitor but broken in the store.
Dimensions are not the same as resolution
People treat pixels and resolution as the same problem, but they aren’t. A file can hit the exact right dimensions and still look weak in search results if the title doesn’t survive at thumbnail size. That is a layout issue, not an export setting. Drawphics ends up rebuilding covers for this more than anything else. Technically correct file, but a design that just does not hold up when it is small.
According to KDP’s official help pages, you can technically get away with an image that is 1,000 pixels on the longest side. But 2,560 pixels for height is the recommendation, and they explicitly say stretching a smaller image to fit will just make it look blurry. For the actual cover file, Amazon caps the size at 50MB.
Paperback: full wrap, and the spine is the variable
You have to upload one PDF. Back, spine, and front, all on a single page. The bleed requirement is 0.125 inches on the top, bottom, and outer edge.
The width changes with every single book. The spine moves based on page count and paper type. That is why there is no single number, and why the question “what size is a paperback cover” does not have an answer you can just paste into a design file.
What the Cover Calculator saves you
KDP’s Cover Calculator does this for you. You enter the trim, page count, paper type, and interior type. It generates a template with the safe zones already drawn. Use it for a first paperback. It removes the arithmetic, and the arithmetic is not the part worth spending a morning on.
The formula, for when a file looks wrong
The formula is still worth having in your back pocket. When a designer sends you a file and the spine looks off, the formula settles it in about ten seconds. That happens more often than it should, usually because the file was built before the interior was final and nobody went back to rebuild it.
Spine is page count times a paper factor. KDP’s help page lists the factors below, plus the full cover formula.
Let’s run a real scenario so you can see how the math actually works. Say you have a 300-page book at 6 by 9 inches, and you chose cream paper. You take those 300 pages and multiply it by the cream paper factor (0.0025). That gives you a spine width of 0.75 inches.
Next, you add the bleed and the covers together. Bleed + back cover + spine + front cover + bleed. That comes out to 13 inches total width. For the height, add the bleed to the trim, which gives you 9.25 inches. If you export that at 300 PPI, your final file needs to be exactly 3,900 by 2,775 pixels. Different numbers in a delivered file mean different inputs. Check before uploading.
Spine text and the 79-page line
You cannot put text on the spine unless the book is at least 79 pages long. If you do add text, keep it pushed in from the edges by 0.0625 inches so it doesn’t wrap onto the front cover during the fold. Under that page count, just leave it blank. It looks better on a thin book anyway.
Hardcover is not the paperback file
The case wrap adds a little over half an inch. The hinge runs about 0.4 inches between the spine and the panels. Anything you put in the hinge is going to fold.
KDP does not publish a hardcover spine formula. The Cover Calculator is the official route, and it has to be generated after the interior is final. If you upload a paperback PDF into a hardcover slot, it gets rejected. A hardcover template cannot be reused if the page count shifts.
Why hardcover files get rebuilt
Drawphics starts from the hardcover template every time. Patching a paperback file takes longer than rebuilding, and the patched version tends to fail anyway.
Worth saying plainly: hardcover is the format where the most files get rebuilt from scratch. It is not because designers get it wrong. It happens because the interior changes after the cover is done, the changes get applied to the paperback, and the hardcover file just sits there, out of date. Nobody notices until the upload.
What actually causes a rejection
Almost never the artwork.
Setup errors, in the order they show up
Spine calculated before the interior was finished. Any page change invalidates it. Missing bleed is another huge one. Design tools export cropped to the artboard by default, so the bleed gets cut, the size check fails, and the file looks fine on your screen. Keep body copy at least a quarter-inch inside the trim line.
Also, do not stretch the eBook cover. Amazon says upscaling does not add quality, and it doesn’t. And finally, make sure you didn’t build a hardcover using a paperback template. The system can tell.
The file size trap
If your file is too large, it simply won’t convert. KDP recommends keeping print covers well under 40MB, but if you export a full-color cover with unmerged layers, you will hit that limit fast.
Two cover files, and nobody separates them
KDP uses two cover images. Confusing them is why product pages look soft.
Upload file versus marketing cover
The file you submit to the portal has a generous cap for Kindle eBooks. But the marketing cover image—the one that actually shows up on the product page—has much tighter rules. It has to be the exact same height and width ratio, but the file size needs to stay under 5MB. JPEG is the safest format here.
Export a big compressed JPEG to stay under the upload limit and the thumbnail can still come out mushy, because the marketing image gets compressed again on display. Size for the smaller target. Look at the title small before uploading. Drawphics runs that check on every cover. The thumbnail is what most readers see first and almost nobody checks it.
White backgrounds disappear
A pale cover on a white page has no edge. If your design is mostly white, it will blend right into Amazon’s background. Add a thin medium gray border around the edge of the image. Even a tiny border is enough to give the book a defined outline.
This is about visibility, not taste. The thumbnail is small in results. A pale cover without a border blends into the page. People scroll past because nothing signals a book. Easy to forget because it looks fine at full size on a desktop.
When the upload fails, check four things
Did the PDF actually include the required bleed, or did your export crop it?
Did the interior reflow after the cover was built? KDP will not fix the spine for you.
Is the file size too large? If it is over the limit, it won’t convert, and if it’s close, you’re asking for a slow queue.
Did you mix up the hardcover and paperback templates? The wrong template gets caught.
Calculator or spreadsheet
Calculator for a first paperback, color interiors, or when you want the safe zones drawn.
Spreadsheet when producing in volume, checking someone else’s file, or when you want the numbers visible. The formula fits in one row.
The one rule that prevents most rejections
Build the cover after the interior is locked. Not before. That one rule prevents most rejections on this page.
FAQ
Is the eBook cover the same file as the paperback?
No. eBook is one RGB image, no spine. Paperback is a CMYK full-wrap PDF with bleed.
Page count changed after the spine was calculated. Now what?
Rebuild. Spine is page count times the paper factor.
What resolution should a KDP cover be?
Print at 300 PPI. eBook images are sized in pixels, and 1,600 by 2,560 matters more than the DPI number.
Does KDP take CMYK for paperback?
It recommends CMYK. PDF/X-1a keeps color and fonts embedded.
How do I resize a cover for KDP?
Crop to 1.6 to 1 at eBook size. Do not stretch. For print, rebuild from the calculator.
Can I use the same spine width for a different page count?
No. The spine moves with page count. A five-page difference on cream paper shifts the cover by about 0.0125 inches, which is enough to print the spine off center.
Does KDP print covers in RGB or CMYK?
Print covers are CMYK. The eBook image stays RGB. Keeping those two straight prevents most color shift complaints.