KDP Margin Calculator
This interactive tool will calculate the exact margins required for your KDP paperback to pass automated review.
How KDP Margins Work
Amazon KDP requires specific margins to ensure your text isn't cut off during the printing and trimming process. The most critical margin is the gutter (the inside margin where the pages are bound to the spine).
The thicker your book (the higher the page count), the larger the gutter must be, otherwise the text will disappear into the crease of the book.
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Format my book →How to Use This Tool
Using the KDP Margin Calculator is straightforward. Enter your estimated page count in the input field above, select your trim size from the dropdown menu, and click Calculate Margins. The tool will instantly display the minimum gutter (inside) margin and the recommended outside, top, and bottom margins for your specific book.
If you are unsure of your page count, use our Word Count to Page Count Estimator to get an estimate first. Remember that your final page count may change slightly during formatting, so it is wise to recalculate margins once your manuscript is fully formatted and you have an exact page count.
The gutter margin is the most critical measurement. This is the inside margin where the pages are bound to the spine. If your gutter is too narrow, readers will struggle to read text near the spine, especially in thicker books. KDP will reject manuscripts that do not meet their minimum margin requirements, so getting this right the first time saves you from frustrating upload failures.
Why Margins Matter for KDP
Margins are not merely an aesthetic choice; they are a technical requirement that directly affects whether Amazon will accept your book for printing. KDP uses automated quality checks during the upload process, and incorrect margins are one of the most common reasons for rejection.
The inside margin (gutter) must increase as your page count grows because thicker books require more space for the binding. A 100-page book needs a smaller gutter than a 500-page book because the pages do not curve as deeply into the spine. Amazon specifies exact minimum gutter widths based on page count ranges, and this calculator applies those exact specifications.
Beyond the technical requirements, proper margins significantly improve the reading experience. Books with generous margins feel more professional and are easier to read for extended periods. In our experience formatting over 500 books for UK authors, we have found that adding an extra 0.1 inches beyond the KDP minimum creates a noticeably more comfortable reading experience without significantly increasing page count.
Common Margin Mistakes UK Authors Make
Using the same margins for every book. Many first-time authors set margins once and reuse them for every project. A 120-page novella and a 400-page epic fantasy require very different gutter margins. Always recalculate for each new project.
Confusing gutter and outside margins. The gutter is the inside margin (closest to the spine), not the outside margin. Setting a large outside margin but a small gutter will result in KDP rejection and unreadable text near the binding.
Ignoring bleed settings for books with images. If your book contains images that extend to the edge of the page (full-bleed images), you need to add an additional 0.125 inches (3.175mm) of bleed on the top, bottom, and outside edges. This calculator shows the text margin requirements; bleed is an additional consideration.
Not accounting for front and back matter. Your total page count includes all pages in the book, including the title page, copyright page, dedication, table of contents, and any blank pages. Make sure you count every page when calculating margins.
Setting margins in centimetres instead of inches. KDP uses inches for all margin specifications. If you are working in a word processor set to metric units, ensure you convert correctly. One inch equals 2.54 centimetres.
For a comprehensive guide to all aspects of KDP formatting, including margins, fonts, and file export, see our complete guide on how to format a book for KDP.
