Paperback Trim Size, Binding and Print: How to Plan Your Book

An ebook reflows to fit any screen. A printed book is a physical object with fixed dimensions, and every decision depends on another: trim size shapes the text block, the text block sets the page count, and the page count sets the spine width and your printing cost. Once you see that chain, you plan in the right order and never rebuild your cover three times.

This guide covers the paperback as self-published authors use it: a perfect-bound softcover, printed on demand or in a short run.

Common trim sizes

Trade paperbacks in the US and UK come in a handful of sizes that readers find familiar. The right choice depends on genre and length: most fiction sits comfortably in the smaller sizes, while non-fiction, workbooks and very long novels move up.

Your print provider decides which sizes you can choose. Amazon KDP offers a fixed list, and so does IngramSpark. Check that the size you want is available with every provider you plan to use, and settle it before you typeset.

Binding and paper

Paperbacks are almost always perfect bound: the pages are glued into the cover at the spine. It is inexpensive and entirely adequate for a novel. Sewn bindings last longer and open flatter, but they are rarely offered in print on demand.

• Cream paper is the norm for fiction. It has less glare and feels warmer.
• White paper suits non-fiction, images and tables.
• Paper thickness decides how thick the book feels. KDP and IngramSpark list a thickness per page for each paper.
• Colour interiors cost far more than black and white. A novel does not need one.
• Cover finish: matte or gloss. Matte looks quieter and more upmarket; gloss makes colours pop.

If you want to add a hardcover, many providers offer one on demand as well, usually a case laminate with the design printed directly on the board rather than a dust jacket. It costs more to produce, needs its own cover with wrap, and normally its own ISBN, because every format is a separate product.

Page count and spine width

Spine width is simply the page count multiplied by the thickness of one page for your chosen paper. You do not need to do the arithmetic yourself: every provider offers a calculator or a cover template generator that gives you the exact dimensions.

Some print processes require the page count to be a multiple of a certain number, at least an even number. Blank pages at the end of a book are therefore perfectly normal.

Bleed and margins

Bleed is extra artwork that extends past the trim line and is cut off after printing. You only need it where images or colour run to the edge of the page. At KDP it is 0.125 in (3.2 mm) on the outer edges. A text-only interior needs no bleed; a cover always does.

Margins decide how comfortable the book is to read. The one that matters most is the gutter, the inside margin: in a perfect-bound book part of each page disappears into the spine. The thicker the book, the wider the gutter needs to be so readers do not have to crack the spine. Providers publish minimum gutters by page count; a well-made book usually goes beyond them.

• Outer and bottom margins a little more generous than the top, so thumbs have room
• A body text size suited to the trim; around 10 to 12 pt is typical for fiction
• Justified text with hyphenation to avoid rivers of white space
• Running heads and page numbers outside the text block
• No widows or orphans, the single stranded lines at the top or bottom of a page

What drives printing cost

With print on demand you pay a fixed charge per copy plus an amount per page. Page count is therefore your biggest lever. A slightly larger trim or a slightly smaller type size can save many pages, but never at the expense of readability. A colour interior multiplies the cost. Exact prices change, so check your provider's current terms (as of 2026).

With an offset print run, the unit price falls as quantity rises, but you pay everything up front and have to store and ship the books yourself. For most self-published debuts, print on demand is the sensible start.

Keep in mind that printing cost and your share together set the retail price. A 500-page paperback printed on demand can end up so expensive that it struggles next to traditionally published titles. Before you raise the price, look again at trim size and margins.

For the wrap itself, read how to design a book cover; for uploading interior and cover, see how to publish on Amazon KDP.

Frequently asked questions

What is the best trim size for a novel?

There is no single best size, but there are proven ones: 5 × 8, 5.25 × 8 or 5.5 × 8.5 in for most fiction, 6 × 9 in for long books and non-fiction. Look at the sizes of comparable recent titles in your genre.

Do I need bleed for the interior?

Only if images or colour run to the edge of the page. A text-only interior needs no bleed. The cover always does.

Can I change the trim size later?

Yes, but it means a new layout: page count, spine width and cover all change. With some providers a different trim size is also a new edition that needs its own ISBN.