KDP Trim Sizes Explained

What trim size means

Trim size is the final size of your book after printing and cutting, written as width x height. A 6" x 9" paperback is 6 inches wide and 9 inches tall. You choose it in KDP when you set up your paperback or hardcover, and your interior file and cover must both be built to match.

Trim size has knock-on effects. A smaller trim fits fewer words per page, so the page count rises. More pages mean a wider spine and, for longer books, a higher printing cost. That is why it is worth choosing your trim size before you format your interior or brief a cover designer.

Standard KDP trim sizes

Regular vs large trim and printing cost

KDP splits trim sizes into two pricing classes. A book counts as large trim if it is wider than 6.12" or taller than 9". Everything else is regular trim. Large trim books cost more to print, which lowers your royalty at the same list price.

Large trim if width > 6.12" or height > 9"

This is why 6" x 9" is so popular. It is the largest common size that still prices as regular trim. The next step up, 6.14" x 9.21", looks almost identical on a shelf but moves into the large trim class.

For short books the gap is smaller but still present: a black ink paperback of 24 to 108 pages costs a flat US$2.30 at regular trim and US$2.84 at large trim on Amazon.com. Read how KDP royalties work for the full printing cost formula.

Choosing a size by genre

There is no required size for any genre, but readers and retailers are used to certain conventions. Matching them helps your book look at home next to similar titles. Here are common choices:

• Novels and general fiction: 5" x 8", 5.25" x 8" or 5.5" x 8.5" are common for a classic paperback feel. 6" x 9" is also widely used and keeps page counts lower.
• Non-fiction, self-help and business: 5.5" x 8.5" and 6" x 9" are the usual picks.
• Memoir and poetry: 5.25" x 8" and 5.5" x 8.5" are popular for a compact, personal feel.
• Textbooks and workbooks: 7" x 10" or 8.5" x 11" give room for diagrams and writing space.
• Journals, planners and coloring books: 8.5" x 11" is the most common, with 6" x 9" for portable journals.
• Children's picture books: square sizes such as 8.25" x 8.25" or 8.5" x 8.5", or 8" x 10".

A practical approach is to look at the top-selling books in your category, note the sizes they use, and then check the print cost for your page count. If two sizes look equally suitable, the regular trim option will usually leave you a higher royalty.

How trim size affects page count

A larger page holds more words, so the same manuscript will have fewer pages at 6" x 9" than at 5" x 8". Fewer pages means a thinner spine and, above 108 pages in black ink, a lower printing cost per copy. On the other hand, a very short book on a large trim can look thin and slight.

Estimate your page count at a few sizes with the KDP Page Count Calculator, and read how many pages should a book have for typical lengths by genre. Remember that margins also change with page count; the KDP Margin Calculator shows the minimum gutter for your book.

Custom trim sizes

KDP also accepts custom paperback trim sizes within a range. Our calculator accepts widths from 4" to 8.5" (101.6 to 215.9 mm) and heights from 6" to 11.69" (152.4 to 296.9 mm). The same large trim rule applies: anything wider than 6.12" or taller than 9" is priced as large trim.

• Custom sizes may limit eligibility for expanded distribution, so check this in KDP if you plan to sell through other retailers.
• Hardcovers are only offered in a short list of standard sizes.
• Your interior PDF and cover must be built to the exact custom dimensions, plus bleed where needed.

Unless you have a strong design reason, a standard size is usually the simpler choice. If your pages include images that run to the edge, read KDP bleed explained before you set up your interior.