Choose a KDP gutter size from the finished page count

Why page count controls the inside margin

A thicker book curves more deeply into the binding, so text needs more room on the inside edge. KDP publishes page-count bands with a minimum inside margin for each band. The current KDP table—not an old screenshot or remembered number—should control the production file you upload.

The inside margin is not the same as bleed. Bleed extends art beyond the trimmed edge; the gutter protects content near the binding. A no-bleed text interior still needs a gutter, and adding bleed does not replace it.

• Confirm the final trim size and whether the interior uses bleed
• Estimate pages from the actual text block, font, leading, and front matter
• Use the current KDP minimum for that page-count band
• Add design room when the minimum produces an uncomfortable text block

The calculation is circular until the layout settles

Page count changes the required gutter, but a larger gutter narrows the text block and can increase page count. If that increase crosses a KDP band, the required gutter changes again. A reliable formatter iterates until the page count and margins stop changing.

Novelbound estimates pages from trim and typography, applies a comfortable layout margin at or above the KDP minimum, and checks the resulting count again. The output remains a production estimate until the exported interior is rendered and inspected.

Verify the interior, not only the numbers

Inspect facing pages at normal reading size. Text should not look trapped in the crease, while outer margins should not make the block appear lopsided. Check chapter openers, long headings, tables, images, and any element that approaches the safe area.

Upload the finished file to KDP's previewer and review every flagged page. Amazon's current specifications and preview decision control acceptance; a calculator reduces preventable errors but cannot replace the platform's final check.