What is the most common trim size for a book?

It depends on the genre, because readers have expectations formed by every book they have already bought in it. Literary and commercial fiction usually run 5.25 × 8 or 5.5 × 8.5 inches, trade non-fiction and memoir 6 × 9, poetry 5.5 × 8.5 or 5 × 8, and workbooks and manuals 7 × 10 or 8.5 × 11. A literary novel at 8.5 × 11 does not read as unconventional; it reads as a report.

How does trim size change my page count?

A larger page holds more words, so it produces a shorter book. The same 80,000-word novel comes out at roughly 300 pages at 5.25 × 8 inches, about 280 at 5.5 × 8.5, and about 240 at 6 × 9.

What trim size should I use outside North America?

A5, which is 148 × 210mm, is the closest common equivalent to 5.8 × 8.3 inches and is what most European printers expect.

How wide should the inside margin be?

It has to grow with the page count, because a thick book does not open flat. As a rough guide for the inside or gutter margin: 0.5 inches under 150 pages, 0.625 inches from 150 to 300, 0.75 inches from 300 to 500, and 0.875 inches or more beyond that.

Can I change the trim size after formatting my book?

You can, but it is the one decision that is expensive to change later, because it alters your page count, and page count sets your printing cost, your spine width and therefore your cover artwork. In Nueel the trim size and margins belong to the design, so changing the trim repaginates the whole book and tells you the new page count before you commit to it.

How to choose a trim size for your book

Trim size is the finished dimensions of a page after the printer cuts the sheet: the “5.5 × 8.5” you pick in a dropdown and then never think about again. It is worth thinking about once, because it is the one decision that is expensive to change later. It alters your page count, and page count sets your printing cost, your spine width, and therefore your cover artwork.

Start from the genre, not from preference

Readers have expectations they could not articulate, formed by every book they have already bought in that genre. A literary novel in 8.5 × 11 does not read as unconventional; it reads as a report.

Genre	Common trim	Why
Literary and commercial fiction	5.25 × 8″, 5.5 × 8.5″	The mass-market paperback proportions readers hold most often
Non-fiction, business, memoir	6 × 9″	Fits more words per page; the standard for trade non-fiction
Poetry	5.5 × 8.5″, 5 × 8″	A narrow measure suits short lines and generous white space
Academic, thesis	6 × 9″, A4	Room for notes, tables and a wide binding margin
Workbooks, manuals	7 × 10″, 8.5 × 11″	Space to write in, and to set diagrams at a usable size

If you are publishing outside North America, A5 (148 × 210mm) is the closest common equivalent to 5.8 × 8.3″ and is what most European printers expect.

Then check what it does to your page count

A larger page holds more words, so it produces a shorter book. That matters more than it sounds. The same 80,000-word novel comes out at roughly:

5.25 × 8″ — about 300 pages
5.5 × 8.5″ — about 280 pages
6 × 9″ — about 240 pages

Print-on-demand pricing is per page, so the larger trim is cheaper to manufacture. It is also thinner, and a thin spine is harder to read on a shelf and feels less substantial in the hand. A novel that comes out under about 120 pages will struggle to carry legible spine text at all.

Choose the trim that makes your book look like the book it is. Then look at the price. Reversing that order produces books that are cheap to print and look it.

The margins are part of the decision

A trim size on its own says nothing about how the page reads. The same 6 × 9 page can hold a comfortable 65-character measure or an exhausting 90-character one, depending on the margins. And the inside margin has to grow with page count, because a thick book does not open flat.

As a rough guide for the inside (gutter) margin:

Under 150 pages: 0.5″
150–300 pages: 0.625″
300–500 pages: 0.75″
Over 500 pages: 0.875″ or more

Getting this wrong is the most common reason a self-published book feels awkward: text disappearing into the spine on a book that will not stay open.

In Nueel, the trim size and the margins belong to the design, so choosing a design sets both to values that suit it. If you change the trim later, the whole book repaginates and tells you the new page count before you commit to it.

Common questions

What is the most common trim size for a book?: It depends on the genre, because readers have expectations formed by every book they have already bought in it. Literary and commercial fiction usually run 5.25 × 8 or 5.5 × 8.5 inches, trade non-fiction and memoir 6 × 9, poetry 5.5 × 8.5 or 5 × 8, and workbooks and manuals 7 × 10 or 8.5 × 11. A literary novel at 8.5 × 11 does not read as unconventional; it reads as a report.
How does trim size change my page count?: A larger page holds more words, so it produces a shorter book. The same 80,000-word novel comes out at roughly 300 pages at 5.25 × 8 inches, about 280 at 5.5 × 8.5, and about 240 at 6 × 9.
Which trim size is cheapest to print?: Print-on-demand pricing is per page, so the larger trim is cheaper to manufacture because it produces fewer pages. It is also thinner, and a thin spine is harder to read on a shelf and feels less substantial in the hand. Choose the trim that makes your book look like the book it is, then look at the price; reversing that order produces books that are cheap to print and look it.
What trim size should I use outside North America?: A5, which is 148 × 210mm, is the closest common equivalent to 5.8 × 8.3 inches and is what most European printers expect.
How wide should the inside margin be?: It has to grow with the page count, because a thick book does not open flat. As a rough guide for the inside or gutter margin: 0.5 inches under 150 pages, 0.625 inches from 150 to 300, 0.75 inches from 300 to 500, and 0.875 inches or more beyond that.
Can I change the trim size after formatting my book?: You can, but it is the one decision that is expensive to change later, because it alters your page count, and page count sets your printing cost, your spine width and therefore your cover artwork. In Nueel the trim size and margins belong to the design, so changing the trim repaginates the whole book and tells you the new page count before you commit to it.
Is the trim size enough to make a page read well?: No. A trim size on its own says nothing about how the page reads. The same 6 × 9 page can hold a comfortable 65-character measure or an exhausting 90-character one, depending on the margins.