By Jesse Wood, founder of Build Until Publishing · November 10, 2026 · 6 min read
Your KDP cover size and spine width come from three numbers: trim size, page count and paper color. The cover is one flat file with the back, spine and front side by side, plus 0.125 inches of bleed on every outside edge. The spine grows with every page, so lock your page count first.
You can do the math by hand in about two minutes, or skip it with the free book specs calculator. Either way, it helps to know what's going on.
You need three facts about your book.
If your page count is odd, add a blank page so it's even. Books print in two-sided sheets, so the count has to be even anyway.
About 0.45 inches on white paper, or 0.5 inches on cream. Spine width grows with every page, and KDP's figures for black and white interiors are about:
| Paper | Spine width per page |
|---|---|
| White | 0.002252 in |
| Cream | 0.0025 in |
Multiply your page count by the number for your paper. Premium color interiors use a slightly different figure, which the calculator handles for you.
For a 200-page book on white paper, that's 200 x 0.002252, or 0.4504 inches. On cream paper it's 200 x 0.0025, or exactly 0.5 inches.
Add the back, spine, front and bleed together. The formula is:
Width = bleed + back cover + spine + front cover + bleed
Bleed is 0.125 inches on every outside edge, so together that's 0.25 inches. The back and front are each one trim width. For a 6 x 9 book with 200 white pages:
The height is simpler: your trim height plus the bleed on top and bottom. That's 9 + 0.25 = 9.25 inches.
So your full cover is about 12.7 x 9.25 inches. At 300 DPI, that's roughly 3,811 x 2,775 pixels.
Keep three areas in mind.
Spines are narrow, and printing isn't perfectly exact. Allow for a small shift, and don't put anything on the spine that would look bad if it moved a hair toward the front or back.
More than you'd think. Seeing the numbers move helps. Here's a 6 x 9 book at three page counts on white paper, using the formula above:
| Pages | Spine | Full cover width |
|---|---|---|
| 100 | 0.2252 in | 12.4752 in |
| 200 | 0.4504 in | 12.7004 in |
| 300 | 0.6756 in | 12.9256 in |
Add 100 pages and the cover grows by about a quarter inch. That's why you shouldn't send the cover to a designer until your page count is final. If an editor cuts ten pages after the cover is done, the spine changes and the wrap has to be redone.
Yes. The Kindle cover is just the front, as a JPG or TIFF in RGB, ideally 2,560 pixels tall by 1,600 wide. A hardcover needs its own cover wrap from KDP's calculator, and it's larger than the paperback's. Don't reuse a paperback wrap for a hardcover. Get the hardcover wrap from KDP's calculator once you know that book's page count, and give your designer both files so each format gets its own correct size.
Yes. Pick your trim size, page count, paper and bleed in our free calculator and it shows the spine width, the full cover size in inches and in pixels at 300 DPI, and the Kindle cover size. It also shows your page size for the interior PDF and your minimum margins. If you switch the same 200-page book to cream paper, the spine becomes 0.5 inches and the full cover about 12.75 inches wide. Try a few page counts before you commit to one.
Use KDP's own cover calculator as the final word. Treat any calculator, ours included, as your planning tool. KDP's own cover calculator gives the official template once you know your page count and trim size. Download its template, hand it to your designer and compare the numbers against what you calculated. If they differ, KDP's numbers win.
When you're ready to check the margins inside the book too, read KDP paperback formatting. If you haven't set up your account yet, the full Amazon walkthrough covers every step in order.
Want your Voice profile and the Acquisitions Board's read on your book before the cover work begins? Start free.
Multiply your page count by 0.002252 inches for white paper or 0.0025 inches for cream paper. A 200-page book on white paper has a spine of about 0.45 inches.
About 12.7 x 9.25 inches on white paper, including 0.125 inches of bleed on each outside edge. That's roughly 3,811 x 2,775 pixels at 300 DPI.
Only if your book has more than 79 pages. Keep the text at least 0.0625 inches away from each spine edge.
KDP prints it at the bottom right of the back cover, so leave a 2 x 1.2 inch space clear there.