Understanding KDP bleed, margins, and safe zones
When you publish a paperback on Amazon KDP, your interior pages are printed on large sheets and then trimmed to your chosen trim size. This trimming process isn't perfectly precise — it can vary by up to 0.0625" from the target cut line. Because of this mechanical tolerance, KDP requires all self-publishing authors to set up their interior files with specific safety zones: the bleed area, the trim line, and the safe content zone.
The bleed area: 0.125" on every side
The bleed area is the 0.125" (one-eighth of an inch) strip that extends beyond the trim line on all four sides of the page. If your interior page has a background color, a full-page image, or any decorative element that should extend all the way to the physical edge of the printed page, that element must extend into the bleed area.
If you don't extend your backgrounds into the bleed zone, the trimming tolerance can leave thin white borders along the edges of your printed pages — an instantly recognizable sign of amateur book design. At 300 DPI, 0.125" equals 38 pixels. So if your trim width is 6 inches (1,800 px), your full-bleed document width should be 6.25 inches (1,875 px).
The safe content zone: 0.25" inside the trim
Just as content can get cut off if it extends to the very edge of your page, it can also appear dangerously close to the edge even if it technically falls within the trim line. KDP recommends keeping all important content — body text, chapter headers, page numbers, and logos — at least 0.25" inside the trim line on all sides.
This 0.25" safe margin, combined with the 0.125" bleed, means your document's safe content box starts 0.375" (113 pixels at 300 DPI) from the edge of the full-bleed canvas. Our calculator gives you the exact coordinates of this safe box for any trim size.
The gutter: why the inside margin needs to be larger
The gutter is the inside margin — the margin closest to the book's spine. When a paperback is bound, the pages wrap into the spine, making the inner edge of each page less visible. The thicker your book, the more the pages curve into the spine, and the larger your gutter needs to be.
KDP publishes specific minimum gutter requirements based on page count. For books under 150 pages, the minimum inside margin is 0.375". This scales up through five tiers, reaching 0.875" for books between 701 and 828 pages. Our calculator highlights the correct tier based on your page count and shows the recommended gutter in both inches and pixels.
How to use these dimensions in design software
In Canva: Create a custom-size design using the "Full bleed width × Full bleed height" values from the calculator. Canva will automatically handle the bleed area when you export as PDF Print, selecting "Crop marks and bleed."
In Adobe InDesign or Affinity Publisher: Set your page size to the trim dimensions and configure bleed to 0.125" on all sides in the document setup. The software will manage the bleed canvas for you.
In Photoshop or Procreate: Create a new document at the full-bleed pixel dimensions at 300 DPI. Place guides at 38px (trim line) and 113px (safe zone) from each edge.
Color books vs. black and white interiors
The bleed and margin dimensions are identical for both color and black-and-white paperback interiors. The distinction affects KDP's printing cost and royalty calculation, but not the page setup specifications. If you're publishing a coloring book, children's book, or illustrated guide that needs full-bleed color images, the same 0.125" bleed rule applies.
Common mistakes to avoid
The most frequent KDP interior upload errors are: (1) using the trim size as the document canvas instead of the full-bleed size, (2) placing text or important graphics within the 0.25" safe zone, (3) submitting at 72 or 96 DPI instead of 300 DPI, and (4) forgetting to account for the gutter on the inside margin. Our calculator prevents all four by giving you the complete set of dimensions in one place.