Standard vs Custom KDP Sizes: Which Should You Use?

When you’re ready to publish a book on Amazon KDP, one of the first technical choices you’ll face is: should I use a standard trim size or a custom one?

It seems like a small detail — but the size of your book affects everything from how professional it looks to how much it costs to print.

In this article, we’ll compare standard vs custom KDP sizes, outline when to use each, and show you the easiest way to apply them in Google Docs using a free add-on.

What Are Standard KDP Trim Sizes?

Amazon offers a set of pre-approved standard trim sizes, which are commonly used for fiction, nonfiction, workbooks, and large print.

Here are a few of the most popular:

If you choose one of these sizes, your manuscript and cover are more likely to pass KDP's checks without issue.

What Are Custom KDP Sizes?

Amazon also allows custom sizes — as long as they meet certain limits:

• Minimum: 4" x 6"

• Maximum: 8.5" x 11.69"

These are useful when:

• You want your book to stand out with a unique format

• You’re replicating an existing book series layout

• You’re producing a niche product like a planner, logbook, or guided journal

With a custom size, you’ll need to upload both your interior and cover files sized exactly to match. KDP won’t adjust or reformat them for you.

Pros & Cons: Standard vs Custom Sizes

For 90% of authors, standard sizes are simpler and safer. But if you need something unique — or your book needs more vertical or horizontal space — a custom size may be worth the extra effort.

How to Format for KDP Sizes in Google Docs

Google Docs doesn’t offer any KDP trim sizes by default — not even 6" x 9". And manually entering custom dimensions often leads to misalignment or export errors.

That’s why we built the KDP Doc Sizer™ Add-On — a one-click tool that lets you instantly apply both standard and custom KDP sizes, right inside Google Docs.

👉 Install KDP Doc Sizer™ on Google Docs

Using KDP Doc Sizer™ to Apply Sizes

For standard sizes:

1. Open your Google Doc.

2. Go to Extensions > KDP Doc Sizer > Open.

3. Choose from the list of built-in KDP sizes (e.g. 6 x 9, 8.5 x 11).

4. Click to apply the layout and margins.

For custom sizes:

1. Select “Custom Size” in the add-on sidebar.

2. Enter your desired width and height (in inches or cm).

3. Adjust top, bottom, left, and right margins.

4. Click “Apply” — and your Google Doc is ready.

You can choose between inches and centimeters depending on your region.

When Should You Use Custom Sizes?

Use a custom size if:

• You're matching the dimensions of a previously published book

• You're producing a logbook, planner, or guided journal

• You want your book to stand out visually

• You’re publishing for a specific niche with layout needs (e.g. 7" x 10")

Use a standard size if:

• You're publishing your first book

• You're unsure what size to choose

• You want to minimize formatting errors and upload issues

If in doubt — go with 6" x 9", the most widely accepted and reader-friendly trim size on Amazon KDP.

Final Thoughts

Your book’s trim size affects its readability, professionalism, and print cost. Whether you’re sticking with a tried-and-true layout or choosing something more unique, the key is to format your manuscript precisely — and make sure it passes KDP’s print checks on the first try.

Using Google Docs? Don’t mess with templates or page setup menus. Let KDP Doc Sizer™ handle the layout in seconds.

👉 Get KDP Doc Sizer™ in the Google Workspace Marketplace