Trim size and margin guide
Bleed, margins and gutter for every KDP trim size.
Inside margin (gutter) for your page count
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| Trim size | Millimetres | Common for |
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Why the gutter changes
A perfect-bound book does not open flat. The thicker the block, the more of the inside edge disappears into the curve, so KDP asks for a wider inside margin as the page count climbs. Outside margins stay the same throughout.
Bleed only matters if ink touches the edge of the page. If it does, extend the artwork 0.125 in past the trim on the top, bottom and outer edge — never on the spine edge.