Two decisions made early in a paperback project ripple through everything else: the trim size and the paper. Trim size is the finished size of the page. Paper type, together with the ink choice, decides how the book feels in the hand, what it costs to print and how thick the spine is. Both feed straight into your page count, your royalty and your cover. This guide explains the options on Amazon KDP, which trim sizes suit which books, how to choose between white and cream paper and between black-and-white and colour, and how those choices change the spine. The last section shows how to set them in Quillen's cover editor.
The short answer
For a typical novel, choose 5.5 x 8.5 or 6 x 9 inches with cream paper, black-and-white ink. For nonfiction, 6 x 9 on white paper is the standard. For a photo book or illustrated children's book, use a larger trim and a colour option. Pick the trim size first, because changing it later changes the page count and the cover. In Quillen, the paperback cover editor lists KDP's trim sizes and paper options and calculates the spine for you.
Trim sizes
KDP offers many paperback trim sizes. These are the ones Quillen's cover editor supports, in inches:
| Group | Sizes (width x height) | Typical use |
|---|---|---|
| Compact fiction | 5 x 8, 5.06 x 7.81, 5.25 x 8 | Genre fiction, novellas, poetry |
| Standard trade | 5.5 x 8.5, 6 x 9, 6.14 x 9.21 | Most novels and general nonfiction |
| Larger trade | 6.69 x 9.61, 7 x 10, 7.44 x 9.69, 7.5 x 9.25 | Nonfiction, textbooks, workbooks |
| Large and square | 8 x 10, 8.5 x 8.5, 8.25 x 8.25, 8.5 x 11, 8.25 x 6 | Photo books, children's books, journals, manuals |
Smaller trims make a book feel quick and portable, but produce more pages (and so a thicker, costlier book) for the same word count. Larger trims feel more substantial and make fewer pages, but cost more per copy and can feel less like a novel. Look at the bestsellers in your genre in a bookshop, and aim for what readers expect.
Paper and ink
KDP paperbacks offer these combinations, and Quillen includes all four:
| Option | Looks like | Best for | Cost |
|---|---|---|---|
| Black and white, white paper | Crisp, bright pages | Nonfiction, textbooks, workbooks, anything with diagrams | Lowest |
| Black and white, cream paper | Warm, softer pages | Novels and memoirs | Lowest |
| Standard colour | Colour on white paper | Colour interiors on a budget | Higher |
| Premium colour | Richer colour on white paper | Photo books, art books, children's picture books | Highest |
Cream paper is the traditional choice for fiction because it is easier on the eyes for long reading and gives the book a classic look. White suits books with illustrations or charts, where the brightness helps clarity. Colour printing costs more per page, and in print on demand that cost comes straight out of your royalty, so use it only when the book needs it.
How the choices change the spine
Each paper type has a thickness, so spine width equals page count times the thickness per page. Quillen uses the figures from KDP's cover guidance:
| Paper option | Spine thickness per page |
|---|---|
| Black and white, white paper | 0.002252 inch |
| Standard colour, white paper | 0.002252 inch |
| Black and white, cream paper | 0.0025 inch |
| Premium colour, white paper | 0.002347 inch |
So a 300-page cream-paper book has a spine of 300 x 0.0025 = 0.75 inch. We cover this in detail in how to calculate spine width. Remember that KDP will not print spine text on very thin books, so a short novella may need a plain spine.
Cover finish
KDP also asks you to choose a matte or glossy cover finish. Matte feels softer and hides fingerprints; glossy makes colours pop and suits bright, illustrated covers. Choose the finish when you set up the book in KDP, not in your cover file.
Page count limits
KDP paperbacks need at least 24 pages (and at least 79 for spine text) and at most 828, and the count is rounded up to an even number. If your book is very short, a larger font or trim can bring it to a sensible thickness; if it is very long, a smaller trim or thinner paper keeps the spine manageable, or consider splitting it into two volumes.
A worked decision
Say you have a 90,000-word fantasy novel. Your readers expect a trade paperback. You choose 5.5 x 8.5 inches, cream paper, black and white. The word count gives you roughly 330 pages, so the spine is about 0.83 inch. If you had chosen 5 x 8 instead, the page count would rise to roughly 380 pages and the spine to about 0.95 inch, with a higher print cost. Both are fine; the choice is about the feel and the price.
Common mistakes
| Mistake | Problem | Fix |
|---|---|---|
| Choosing a trim size after the cover | The spine and cover width are wrong | Choose first |
| White paper for a novel without thinking | Harsher to read, less traditional | Consider cream |
| Colour for a text-only book | Needless cost | Use black and white |
| Ignoring page count when choosing a trim | Surprises in cost and spine | Estimate pages for each size |
| Assuming spine text will print on a thin book | KDP will not print it on very short books | Check the page count |
| Not matching the interior and cover settings | The cover will not fit | Use the same trim and paper for both |
Do it in Quillen
Quillen's paperback cover editor holds the trim size and paper settings and calculates the spine and the full cover width for you.
- Open the editor. Click Cover in the header and choose Paperback cover.
- Choose the trim size. Under Print settings, use the Trim size menu.
- Choose the paper and ink. Use the Paper / ink menu: black and white on white paper, black and white on cream paper, premium colour or standard colour.
- Set the page count. Click Re-estimate from manuscript to estimate it from your book, or type your own. Quillen explains that the estimate is based on your manuscript's layout and that you should confirm it against the count KDP shows after you upload the interior.
- Read the results. The panel shows the spine width, the full cover size, the size in pixels at 300 DPI, and whether spine text is allowed.
- Change an option to compare. Switch to a different trim or paper, and watch the spine and cover width update.
If KDP's error message gives a different cover size from the one the editor calculates, use the Override full cover width option to enter the size KDP asks for. We cover that case in how to fix a KDP cover size error.
Checklist
- Trim size chosen to match the genre and decided before the cover.
- Paper chosen for the content: cream for fiction, white for illustrations.
- Black and white unless the book needs colour.
- Page count estimated, then confirmed against KDP's count.
- Spine checked, and spine text only on books thick enough.
- Interior and cover settings identical.
Common questions
What trim size should I use for a novel?
Most novels use 5.5 x 8.5 or 6 x 9 inches. Genre fiction often uses 5 x 8 or 5.25 x 8. Look at bestsellers in your genre.
Should I use cream or white paper?
Cream is traditional for fiction and easier on the eyes for long reading. White suits nonfiction, workbooks and books with illustrations or charts.
How does paper type change the spine?
Spine width is the page count times the thickness per page: 0.002252 inch for white paper (black and white or standard colour), 0.0025 inch for cream, and 0.002347 inch for premium colour.
What trim sizes does Quillen support?
Quillen's paperback cover editor supports 15 KDP trim sizes from 5 x 8 up to 8.5 x 11, including 6 x 9, 5.5 x 8.5 and several square sizes.
Can I change the trim size later?
You can, but it changes the page count and so the spine and cover. Decide first, and use the same trim size for the interior and cover.