Formatting · Topic 3 of 5
Gutter
What to do
Add extra inside-margin space (the "gutter"), on the side of the page nearest the spine, so text doesn't disappear into the binding.
Why it matters
When a book is bound, some of the inner margin gets absorbed by the curve of the pages near the spine. Without a gutter, text on the inner edge can be difficult to read or partially hidden once the book is glued or sewn, readers have to crack the spine open just to see the words closest to the middle.
Steps for your program
Choose a program to see its workflow. Menus can differ between versions.
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Common mistakes to avoid
- Adding gutter space to only one side of the page instead of using mirrored margins, this looks fine on odd pages and wrong on even pages (or vice versa).
- Confusing gutter with your general inner margin and doubling up (very wide unusable margin) or skipping it entirely (text crowds the spine).
- Not adjusting the gutter when the page count changes significantly after edits, a book that grew from 120 to 280 pages likely needs a wider gutter.
Completion checklist
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What does this mean? What is the gutter?
What is the gutter?
The gutter is space near the binding that keeps text from disappearing into the spine. Some programs treat it as part of the inside margin; others offer an extra Gutter setting.
Try this: Do not automatically add the same amount in both places. Follow the instructions for your program and printer, and check the total inside space. KDP’s Word workflow can use the inside-margin setting with the separate Gutter field at zero.
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What does this mean? What are mirror margins?
What are mirror margins?
Mirror margins make inside and outside margins swap sides on alternating pages, like the two pages of an open printed book.
Try this: The inner edge of a left-hand page is on its right. The inner edge of a right-hand page is on its left. Book-layout programs may manage facing pages automatically rather than offering a switch called Mirror margins.
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What does this mean? What are facing pages?
What are facing pages?
A spread is a left page and a right page viewed together. Looking at spreads helps you see whether the text sits comfortably on both sides of the binding.
Try this: Preview several middle spreads and chapter openings. Look for text too close to the center. A screen preview helps, but inspect a physical proof before approving a printed edition.
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Troubleshooting
How do I know if my gutter is too small?
Print a sample page (or a physical proof copy) and check whether text near the inner edge is hard to read without pressing the book flat. If so, increase the gutter and re-check your printer's minimum for your updated page count.
My word processor doesn't have a 'gutter' field, what do I do?
Use mirrored inner/outer margins instead: set your inner margin to (base inner margin + desired gutter amount) and keep the outer margin at your normal size. The effect is the same even without a dedicated gutter field.
Reference: KDP’s trim size, bleed, and margin requirements. Check your chosen printer’s current specifications for your edition.