Amazon KDP book trim sizes and margins: 6×9, 5.5×8.5, A5 and more

You choose the trim size when you upload your Word file. There are 18: 5×8, 5.06×7.81, 5.25×8, 5.5×8.5, A5 (14.8×21 cm), 6×9, 6.14×9.21, 6.58×9.47 (≈16.7×24 cm, the size of the reference novel), 6.69×9.61, 7×10, 7.44×9.69, 7.5×9.25, 8×10, 8.25×6 (landscape), 8.25×8.25 (square), 8.27×11.69 (A4), 8.5×8.5 (square) and 8.5×11.

The most popular: 6×9 for nonfiction, 5.5×8.5 for novels and 8.5×11 for illustrated or activity books.

Ask for bigger or smaller margins, for the whole page or for a specific side (top, bottom, inside or outside). You can give an exact measurement or describe it relative to the current one (“a bit smaller”).

Gutter always respects the minimum Amazon KDP requires for your page count. If you ask for something that doesn't fit, it tells you and suggests the closest value that does.

Gutter does. The inside margin (the one by the spine, where the book is bound) increases with the page count, as KDP requires, so it can't accidentally end up below the minimum. The actual spine width for your cover is calculated from the page count and the paper type (white or cream).

In novels, margins are “mirrored”: the inside margin (by the spine) is always the largest and the outside margin the smallest, and they swap between even and odd pages, just like in a printed book.