Free Book Mockups by KDP Trim Size — 6x9, 5.5x8.5, 5x8 & Square

KDP Select paid out $67.0 million to authors in June 2026 alone. Behind every one of those payouts is a product page, and on every product page is one image doing most of the selling.

Here is the problem almost nobody talks about: that image is usually the wrong shape.

Amazon KDP's default trim size is 6" x 9" — it is the most common trim size for books in the U.S. and the size KDP pre-selects for you in Print Options. So the internet is flooded with 6x9 mockups. But if you published a 5" x 8" novel or an 8.25" x 8.25" children's book and you drop your cover into a 6x9 mockup, you have just shown readers a book with the wrong proportions. Your spine is too thick. Your cover is too narrow. The type sits at a scale it will never sit at in a reader's hands.

This guide fixes that. Every mockup below is grouped by the KDP trim size it actually matches, with the real print specifications for that size alongside it.

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First: Know Your Trim Size

Trim size is your printed book's finished width and height, always written width x height.

Two numbers from KDP's own documentation matter before you pick anything:

The large trim threshold. Any book more than 6.12 inches (155.5 mm) wide more than 9 inches (228.6 mm) tall is classified as a large trim size, and it carries a different printing cost than a regular trim size. This is why 6x9 is so dominant — it sits exactly at the ceiling of the regular tier.