Last reviewed by Robert Prime — May 2026
Quick Answer: KDP's inside (gutter) margin scales with page count: 0.375" for 24-150 pages, 0.5" for 151-300, 0.625" for 301-500, 0.75" for 501-700, 0.875" for 701-828. Use our free gutter calculator to verify.
Full reasoning, why-it-happens, and the exact fix below.
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We see this come through our formatting queue at publishing.co.uk regularly, so the patterns and fixes here are based on what actually works at upload.
What this error means
KDP's automated pre-flight checker measures the live text area on every page and compares it to the minimum margins published for your trim size and page count. If any page has a gutter (inside margin) below the threshold, or an outside, top, or bottom margin below 0.25", the file is bounced before a human ever looks at it. The error usually reads something like "Your manuscript's margins do not meet our minimum requirements" with the specific page numbers listed.
The most common trigger is the gutter, because most authors don't realise it scales with page count. A 250-page novel needs a 0.5" gutter — not the 0.375" Word ships with by default. Books over 700 pages need a hefty 0.875" gutter so binding glue doesn't swallow your text.
📎 Source: KDP's authoritative documentation on this rule is at KDP's official margin specifications.
Why it happens
Three workflows cause 90% of margin rejections.
First, Microsoft Word defaults. Word's "Normal" template uses 1" margins all round and no gutter at all. Authors who pick "Book Fold" still get a generic 0.5" gutter that's too small for long manuscripts.
Second, template mismatch. Authors download a 6x9 Vellum or Atticus template designed for a 200-page book, then write a 450-page manuscript. The template's gutter — fine at 200 pages — is now below KDP's 0.625" floor for 301–500 page books.
Third, Canva and Affinity Publisher interior exports. Both tools let you design beautiful pages but neither warns you when margins drop below KDP's spec. Canva's "book" preset uses a 0.5" gutter regardless of page count.
InDesign users hit this when "Mirror margins" is off and the gutter is split between left and right pages instead of doubled on the inside edge.
The fix
Step 1: Open your manuscript and check the final page count. Round up to the nearest band.
Step 2: Set the gutter to KDP's minimum for your band — and add 0.125" for safety:
| Pages | KDP minimum gutter | Recommended |
|---|---|---|
| 24–150 | 0.375" | 0.5" |
| 151–300 | 0.5" | 0.625" |
| 301–500 | 0.625" | 0.75" |
| 501–700 | 0.75" | 0.875" |
| 701–828 | 0.875" | 1.0" |
Step 3: Set outside to at least 0.25". If your interior has bleed (any image touching the page edge), top must be 0.375" minimum.
Step 4 (Word): Layout → Margins → Custom Margins → set "Gutter" to your target. Make sure "Multiple pages" is set to "Mirror margins". Re-export to PDF using "Save As → PDF" with the "Standard" option (not "Minimum size", which strips fonts).
Step 5 (Vellum / Atticus): Both tools have a margin slider in the export panel. Drag it up and re-export.
Step 6 (InDesign): File → Document Setup → Margins and Bleed. Set "Inside" to your target. Re-export with the PDF/X-1a preset.
Step 7: Open the new PDF in Acrobat or Preview and use the measure tool on the gutter to confirm it's actually applied — some Word exports silently ignore margin changes if the document has section breaks with overridden margins.
How to pre-flight it
Before you resubmit to KDP, drop your PDF into our free KDP Readiness Score. It measures every page's margins against the live KDP table, flags any page that's below spec, and checks the other 30 rules KDP enforces — DPI, embedded fonts, trim mismatch, and the rest. Catching it pre-upload saves the 24–72 hour KDP review cycle.
Related errors
- KDP error: cover trim doesn't match interior
- KDP error: bleed misconfigured for trim size
- KDP error: odd page count
FAQ
Is KDP's gutter the same as the inside margin? Yes. KDP uses "gutter" and "inside margin" interchangeably in their guidelines. It's the extra space added on the binding edge of every page.
Can I use 0.375" gutter on a 300-page book? No — 300 pages falls into the 151–300 band where the minimum is 0.5". You'd be rejected.
Does the gutter need to be larger on hardcover? KDP applies the same gutter minimums to paperback and hardcover, but most binders recommend adding an extra 0.125" on hardcover because the binding is stiffer.
Why is my Word file showing 0.5" gutter but the PDF measures 0.375"? Word sometimes splits the gutter across both pages when "Mirror margins" is off. Toggle it on under Layout → Page Setup → Multiple pages → Mirror margins, then re-export.
Frequently asked questions
Does the outside margin matter as much as the gutter?
Less commonly the cause of rejection, but KDP requires 0.25" minimum on outside for all paperbacks. Use 0.5"+ for comfort.
How do I verify my PDF's margins match KDP's minimums?
Open the PDF and use the measure tool (Adobe Acrobat) or check the page-setup metadata. The free KDP Readiness Score measures every margin automatically and flags any that fall under the minimum for your page count.
Can publishing.co.uk re-margin a manuscript I've already laid out?
Yes — re-margining is one of the most common fixes we do. We adjust the gutter, outside, top and bottom margins to KDP's spec for your trim and final page count, and re-flow the body text accordingly. Usually a 24-hour turnaround.
Does fixing the margins change my page count?
Slightly, yes — wider margins typically push 2-5% more pages onto the manuscript. We model this for your file before re-margining so you know the final spine width before the cover designer locks the wrap.
Related KDP error fixes
If you got the rejection above, you may also want to check these related issues — they tend to cluster:
Full list: KDP formatting errors hub · KDP rejection fixes hub · KDP rejected my book
About this guide
This page is part of a series of UK-focused KDP rejection guides at publishing.co.uk, each documenting a specific reason KDP can reject a print or Kindle file and the exact fix. Written by Robert Prime — founder of publishing.co.uk, co-runs the LoveReading network, and has overseen 500+ KDP submissions through formatting work in this category (margins).
If you'd rather have someone else handle this and the other 35 issues KDP checks for, our formatting service is from £69 with a 3-day turnaround and a 100% KDP-acceptance guarantee.
Run a free KDP Readiness Score on your file before you upload — catches this issue and 35 others, in 60 seconds.
External references
- Amazon KDP Help — official KDP documentation
- Author Earnings reports (ALCS) — UK author income surveys
