Free KDP file checker · no sign-up
KDP rejected your file?
Find out exactly why.
Upload the interior or cover PDF that Amazon KDP sent back. The checker measures the trim size, bleed, margins, page count, spine width, embedded fonts and picture resolution against KDP's published paperback rules, then tells you in plain words what to change.
Your files are checked and deleted straight away. Nothing is kept.
KDP spine width calculator
Spine width and full cover size
Enter the final page count. Odd counts are rounded up, as KDP does.
Spine text is only printed on books of at least 79 pages, and must sit at least 0.0625" from each fold. Groundwood paper is thicker; use KDP's own cover calculator for it.
What it checks
KDP's paperback rules, in one place
Interior PDF
- Trim and bleed. Every page must be the trim size, or the trim plus 0.125" wide and 0.25" tall with bleed. Bleed goes on the outside edge only.
- Page count. At least 24 pages (72 for standard color); the maximum depends on trim and paper.
- Margins. Text kept clear of the gutter, which grows with page count, and of the other three edges.
- Fonts. Every font fully embedded.
- Pictures. Placed at 300 DPI or more.
- Layers. Flattened before export.
Cover PDF
- One page. Back, spine and front together.
- Exact size. Bleed + back + spine + front + bleed wide, and the trim height plus 0.25" tall.
- Spine. Width matched to the page count and paper; no spine text under 79 pages; spine text 0.0625" from the folds.
- Safe area. All text at least 0.125" inside the trim lines.
- Barcode area. Kept clear if KDP is to print the barcode.
- Fonts and pictures. Embedded fonts, 300 DPI pictures.
Minimum inside (gutter) margin by page count
| Pages | Inside margin | Other edges |
|---|---|---|
| 24 to 150 | 0.375" | 0.25" without bleed, 0.375" with bleed |
| 151 to 300 | 0.5" | |
| 301 to 500 | 0.625" | |
| 501 to 700 | 0.75" | |
| 701 to 828 | 0.875" |
Figures from KDP's help pages on trim, bleed and margins and on paperback covers, checked 31 October 2026.
FAQ
KDP rejections, answered
The most common reasons are a page size that does not match the trim size chosen in KDP, bleed added to the wrong edges, text inside the minimum margins (especially the inside margin, which grows with page count), fonts that are not embedded, and too few pages. The checker tests each of these.
Almost always because the cover width does not match the spine for the final page count and paper type, or because text sits too close to the trim lines or the spine folds. A cover built before pages were added or removed is the usual cause.
Page count multiplied by the paper thickness: 0.002252 inches per page for black ink on white paper or standard color, 0.0025 inches for cream paper, and 0.002347 inches for premium color. The full cover width is the bleed (0.125 inches) plus the back cover, the spine, the front cover and the bleed again.
The trim width plus 0.125 inches, and the trim height plus 0.25 inches. KDP adds bleed only to the outside edge, the top and the bottom, so a 6 x 9 book with bleed is 6.125 x 9.25 inches.
An inside (gutter) margin of 0.375 inches for 24 to 150 pages, 0.5 inches for 151 to 300, 0.625 inches for 301 to 500, 0.75 inches for 501 to 700 and 0.875 inches for 701 to 828. The outside, top and bottom margins are at least 0.25 inches without bleed and 0.375 inches with bleed.
No. Each file is checked in a temporary folder and deleted as soon as the check finishes. We keep only a count of checks and of problems found, never the file or its contents.
No checker can promise that. This one tests what can be measured in the file. KDP also reviews content, metadata, blank pages and text that is part of a picture, so always look through the Print Previewer and order a proof copy.
Keep reading
- KDP cover upload errors — why cover files get rejected.
- Why your KDP interior PDF fails validation — what to fix first.
- KDP interior PDF specifications — the full formatting guide.
- How to avoid rejection when uploading low-content books.
Skip the rejections on your next book.
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