A black-ink paperback on KDP can be printed on cream, white or groundwood paper. A book with color ink is always printed on white. The choice changes more than the color of the page: the spine, the cover size and the page limit follow from it.
The three papers side by side
| White | Cream | Groundwood | |
|---|---|---|---|
| Ink | Black, or color | Black only | Black only |
| Weight | 50–61 lb (74–90 GSM) | 50–61 lb (74–90 GSM) | 45 lb (60 GSM) |
| Spine per page | 0.002252″ | 0.0025″ | 0.00235″ |
| Spine at 300 pages | 0.676″ | 0.750″ | 0.705″ |
| Most pages | 828 | 776 | 812 |
| Hardcover | Yes | Yes | No |
KDP notes that paper weight varies with the printing location. The page limits are for the usual trim sizes; some of the largest sizes have lower maximums.
What it costs
White and cream cost the same: KDP gives one price table for both. On groundwood, KDP puts the cost per page about 5% lower.
On Amazon.com, a regular-trim black-ink paperback of 300 pages costs $1.00 plus $0.012 a page on white or cream, which is $4.60. On groundwood it is $1.00 plus $0.0114 a page, which is $4.42. Large trim sizes cost more, and other marketplaces have their own tables.
Which to choose
KDP's only advice on this is that white paper shows images and graphics with higher contrast. Many publishers print novels and memoirs on cream and books with pictures, tables or diagrams on white. That is a convention, not a KDP rule.
Groundwood is the lightest of the three and the cheapest to print. Its pages are slightly thicker than white ones, so its spine is a little wider. A book of color pictures cannot use it, and neither can a hardcover.
The paper changes the spine
Spine width is the page count times the figure for the paper. The same 300 pages are 0.676″ on white and 0.750″ on cream, so a cover made for one paper does not fit the other. The paper also decides from how many pages a line of spine text fits; see KDP minimum page count and spine text.
KDP lets a black-ink paperback switch between certain papers after it is published. Make the cover again for the new paper before you switch, since the spine width changes with it.
What Torcul does
You choose the paper on Torcul's design screen. The spine width, the full cover size and whether spine text fits are all worked out for that paper. The free spine calculator gives the same figures for any page count.
Sources
- Print Options
- Groundwood Paper
- Paperback Submission Guidelines
- Paperback Printing Cost
- Set Trim Size, Bleed, and Margins
None of this guarantees that KDP will accept a file. KDP changes its help pages and its prices, so check the date on this one and on any report a tool gives you.