KDP's paperback guidelines cap the interior upload at 650 MB — for the whole file, not per page or per image. There's no stated minimum, and KDP notes there's no set maximum image DPI either, though it warns that excessively high resolution can cause processing timeouts or manufacturing delays rather than better print quality.
What the limit covers
| Limit | Applies to | Source |
|---|---|---|
| 650 MB | Total size of the uploaded interior file | KDP paperback submission guidelines and image formatting guidance |
| No stated maximum DPI | Individual images | KDP notes excessive resolution risks processing timeouts or manufacturing delays instead |
The 650 MB number is the same limit stated on both KDP's submission guidelines and its image-formatting guidance page — it's the ceiling for the finished interior PDF as a single upload, regardless of how many pages it contains.
Why a coloring book interior rarely gets close
A 1-bit image — pure black, pure white, no gray values in between — compresses far more efficiently than a photo or a grayscale scan, because there's so little visual information per pixel to encode. A 300 DPI, 8.5 × 11 in page at 1-bit is a small file relative to the same page saved as a full-color or grayscale image at the same pixel dimensions. Stacked across CrayonMill's full 24–300 interior-page window — or any page count KDP allows — a properly exported 1-bit coloring book interior sits well under the 650 MB ceiling — the limit isn't something a well-formed coloring book file needs to plan around.
Where it actually becomes a risk
The 650 MB ceiling matters when something in the export pipeline goes wrong, not from page count on its own: pages accidentally left in grayscale or full color instead of 1-bit, images exported at a resolution far higher than 300 DPI needs, or embedded color profiles and metadata bloating file size without adding anything visible. Any of those can push a file size up without changing how the book looks, which is also why KDP frames very high resolution as a processing risk rather than a quality benefit — bigger isn't safer once a page already clears the DPI recommendation.
How this relates to the other interior checks
File size sits alongside, but separately from, the checks that actually determine whether pages print correctly — resolution, 1-bit color depth, gutter, and safe margins (see the interior PDF checklist guide for all six). A file well under 650 MB can still fail review for gray edge pixels or a wrong gutter; a file that happens to be large isn't automatically wrong on those other checks either. It's one more thing to have right, not a substitute for the checks that actually govern print quality.
What CrayonMill exports
Every page CrayonMill generates is cleaned to 1-bit before it reaches the export step, which is what keeps even a full 300-page interior file well under KDP's 650 MB ceiling without any manual compression step. The export check doesn't include a file-size warning because, at 1-bit and KDP's allowed page-count range, the ceiling isn't something a book built through the normal pipeline can realistically reach.
Sources
Last verified 2026-09-04. Updated 2026-09-04.