What is book size (trim size), and how do you choose it?

Book size, known in the trade as trim size, is the width and height of a page in the printed book after trimming. It determines how many pages the book will have, what printing will cost, and how it will feel in the hand. Most authors don't need to invent anything: pick a common size for your genre, and check that it also suits the translated edition.

What book size actually is

When a print shop prints a book, it prints on large sheets and then cuts them. The size left after the cut is the trim size. In the United States it's measured in inches, so you'll see numbers like 6×9 or 5×8.

The size affects three things:

• How the book looks. A small novel that's easy to carry in a bag, or a wide, dignified nonfiction book.
• How many pages it has. A small page holds fewer words, so the book comes out thicker.
• How much printing costs. More pages, or an extra-large page, cost more.

Which sizes Amazon offers

KDP (Amazon's self-publishing platform) lays out the options on its help page about trim size. According to that page, "the most common trim size for books in the US is 6 x 9 inches," and it's also the default when you set up a new printed book.

For hardcover, Amazon offers a few fixed sizes: 5.5×8.5, 6×9, 6.14×9.21, 7×10 and 8.25×11. The last three count as "large."

You can also choose your own size, with a width between 4 and 8.5 inches and a height between 6 and 11.69 inches. Just note that a book wider than 6.12 inches or taller than 9 inches counts as "large," and according to Amazon it has a different printing cost.

How to choose a size for your book

The simplest way: go to the shelf. Take three books from your genre that look right to you, and measure them. If all three are about the same size, that's probably your answer.

A few rules of thumb:

• A novel or memoir usually comes in a medium size, easy to hold in one hand.
• A nonfiction book or guide with lots of tables and headings gains from a wider page.
• An illustrated children's book is a world of its own, and sometimes needs a square or extra-wide size.
• A poetry book looks good on a narrow page, which keeps the lines whole.

One more thing worth knowing: every size has an allowed page range. According to Amazon, a paperback in 5×8 with black ink on white paper can have between 24 and 828 pages, and most hardcover sizes are limited to 75 to 550 pages. A very thick book needs a size that allows it.

What changes when the book is translated

The size itself doesn't have to change. What changes is the page count. Different languages take up different amounts of space: Hebrew text translated into English or French usually comes out longer. We wrote about it in why page count changes in translation.

So before you decide on a size for the translated edition, it's worth waiting for the final text. A book that fits nicely in 200 pages in Hebrew can pass 240 in English, and the spine of the cover needs to be wider accordingly.

Another question: keep the same size in every language or not? If you sell mostly through one store, like Amazon in the United States, it makes sense to follow what's common there. If the editions will stand side by side, say at a conference or in a bookstore, a uniform size looks tidier.

And what about the digital book?

A digital book has no fixed size. The text flows to fit the reader's screen, whether it's a phone, a tablet or a Kindle. Book size is a print question only. The difference between a flowing book and a fixed-layout book is explained in reflowable or fixed-layout ebook.

Before you approve

After you've chosen a size, order a printed proof copy and hold it in your hand. What looks good on the screen doesn't always feel right in practice. A checklist for such a copy is waiting in the proof copy checklist for a translated book.