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Can you change the trim size of a published KDP book?

What you can and can't change after publishing

KDP splits your book's settings into fields you can edit any time and fields that are locked the moment the print edition goes live:

• Editable, no penalty: interior file, cover file, ink & paper type, description, keywords, categories, and price. Updating any of these never touches your reviews or your ASIN — the book just goes back through review for a day or so.
• Locked forever: trim size, title and subtitle, author name, language, and the ISBN itself. Print ISBNs are registered in external databases with those exact attributes, so this is an ISBN-system constraint, not just an Amazon rule.

So the direct answer to "will changing my book size erase my reviews?" is: changing size requires a new book, and it's the new-book part that puts your reviews at risk.

Where reviews actually live

Reviews attach to the Amazon detail page family, not to your manuscript or your KDP account. All linked editions of the same work — Kindle, paperback, hardcover, audiobook — pool their reviews on one shared detail page. That's why a Kindle review shows up on the paperback page and vice versa.

Two scenarios follow from that:

• You have another live edition (usually Kindle). Keep it live. When your new-trim paperback publishes, it should link to the same detail page — the family's reviews display on the new paperback too. If linking doesn't happen automatically within a few days, contact KDP support and ask them to link the editions; it's a routine request.
• The paperback is your only edition. The new ASIN starts at zero reviews. The old listing doesn't vanish when you unpublish (third-party sellers can keep it alive), but it stops earning you anything, and its reviews stay stranded on it.

The republish playbook

1. Re-lay out the interior at the new trim. Page count will change, which changes your printing cost and royalty — check the numbers with the paperback royalty calculator before you commit.
2. Rebuild the cover. A new trim and new page count mean a completely different wrap: new spine width (calculate it here), new total dimensions, new bleed. Your old cover file will be rejected or print wrong.
3. Create the new title on your bookshelf with the new trim, and publish it.
4. Link editions. Confirm the new paperback shares a detail page with your Kindle edition. This is the step that preserves your reviews.
5. Unpublish the old paperback only after the new one is live and linked. Don't delete it — unpublishing is reversible, deleting is not.

Frequently asked

Will I lose my sales rank and history?

On the print edition, yes — rank is per-ASIN and the new ASIN starts fresh. Your Kindle edition's rank is unaffected.

Does this apply to hardcovers too?

Yes. Trim size is locked on every print format. Kindle ebooks have no trim size at all.

Is it worth doing?

Usually only if the current size causes real problems — printing cost too high at your page count, reader complaints, or a series whose volumes don't match on a shelf. "I'd pick differently today" is rarely worth resetting a print ASIN over.

Can KDP support just change it for me?

No. Support can link editions and fix listing issues, but no one can edit a locked field on a live print book — not even Amazon.