The following info is from this KDP Page on how to format a paperback book. Click and read the rest of the material and the videos as well. Also watch the excellent video below from KDP University
- Trim size. Your printed book’s width and height. The most common trim size for paperbacks in the U.S. is 6″ x 9″ (15.24 x 22.86 cm), but you have several other options.
- Bleed. Bleed is a printing term that refers to when printed objects on a page, such as images, background color, or graphics, extend past where the publication will be trimmed. This ensures that your printed objects reach all the way to the edge of the page. When a book is printed, all pages are trimmed to the selected trim size by cutting 0.125” (3.2 mm) from the top, bottom, and outside edges. In order for objects on your page to reach all the way to the edge of the page, those objects must extend past where the page will be trimmed by 0.125” (3.2 mm). Accounting for bleed is important because it prevents a white border from appearing at the edge of the page when the book is trimmed. The video and step-by-step instructions explain how to set page size and margins for books with and without bleed. For more information on bleed see our Print Options Help page.
- Margins. Every page has three outside margins (top, bottom, and side) and one inside margin (also called the gutter). Margins ensure your text isn’t cut off during manufacturing. Set your page size before you set your margins. Why? Margin size depends on page count and on whether you have elements that bleed. See this chart to find your margin size:
Page count Inside (gutter) margins Outside margins (no bleed) Outside margins (with bleed) 24 to 150 pages 0.375 in (9.6 mm) at least 0.25 in (6.4 mm) at least 0.375 in (9.6 mm) 151 to 300 pages 0.5 in (12.7 mm) at least 0.25 in (6.4 mm) at least 0.375 in (9.6 mm) 301 to 500 pages 0.625 in (15.9 mm) at least 0.25 in (6.4 mm) at least 0.375 in (9.6 mm) 501 to 700 pages 0.75 in (19.1 mm) at least 0.25 in (6.4 mm) at least 0.375 in (9.6 mm) 701 to 828 pages 0.875 in (22.3 mm) at least 0.25 in (6.4 mm) at least 0.375 in (9.6 mm)
