KDP spine width calculator
Spine width is the page count times the paper thickness: 0.002252 in per page on white paper, 0.0025 in on cream, 0.002347 in for premium colour.
| Measurement | Value |
|---|---|
| Spine width | 0.6756 in (17.16 mm) |
| The sum | 300 x 0.002252 in |
| Text on the spine | Allowed (79 pages or more) |
| Full cover size with bleed | 12.926 x 9.25 in |
| Full cover size, millimetres | 328.3 x 235 mm |
| Full cover size, pixels at 300 DPI | 3878 x 2775 px |
Source: KDP help, Create a Paperback Cover. Read on 10 November 2026.
The cover page gives the width as "Bleed + Back Cover Width + Spine Width + Front Cover Width + Bleed" and the height as "Bleed + Trim Height + Bleed", with 0.125 in of bleed. The full cover size above is that sum for your trim size. Millimetres and pixels are converted here.
Spine width by page count
| Page count | White paper | Cream paper | Standard colour | Premium colour |
|---|---|---|---|---|
| 24 | 0.054 in (1.37 mm) | 0.06 in (1.52 mm) | under the 72-page minimum | 0.0563 in (1.43 mm) |
| 50 | 0.1126 in (2.86 mm) | 0.125 in (3.18 mm) | under the 72-page minimum | 0.1174 in (2.98 mm) |
| 79 | 0.1779 in (4.52 mm) | 0.1975 in (5.02 mm) | 0.1779 in (4.52 mm) | 0.1854 in (4.71 mm) |
| 100 | 0.2252 in (5.72 mm) | 0.25 in (6.35 mm) | 0.2252 in (5.72 mm) | 0.2347 in (5.96 mm) |
| 150 | 0.3378 in (8.58 mm) | 0.375 in (9.53 mm) | 0.3378 in (8.58 mm) | 0.3521 in (8.94 mm) |
| 200 | 0.4504 in (11.44 mm) | 0.5 in (12.70 mm) | 0.4504 in (11.44 mm) | 0.4694 in (11.92 mm) |
| 250 | 0.563 in (14.30 mm) | 0.625 in (15.88 mm) | 0.563 in (14.30 mm) | 0.5868 in (14.90 mm) |
| 300 | 0.6756 in (17.16 mm) | 0.75 in (19.05 mm) | 0.6756 in (17.16 mm) | 0.7041 in (17.88 mm) |
| 400 | 0.9008 in (22.88 mm) | 1 in (25.40 mm) | 0.9008 in (22.88 mm) | 0.9388 in (23.85 mm) |
| 500 | 1.126 in (28.60 mm) | 1.25 in (31.75 mm) | 1.126 in (28.60 mm) | 1.1735 in (29.81 mm) |
| 600 | 1.3512 in (34.32 mm) | 1.5 in (38.10 mm) | 1.3512 in (34.32 mm) | 1.4082 in (35.77 mm) |
| 700 | 1.5764 in (40.04 mm) | 1.75 in (44.45 mm) | over the 600-page limit | 1.6429 in (41.73 mm) |
| 776 | 1.7476 in (44.39 mm) | 1.94 in (49.28 mm) | over the 600-page limit | 1.8213 in (46.26 mm) |
| 828 | 1.8647 in (47.36 mm) | over the 776-page limit | over the 600-page limit | 1.9433 in (49.36 mm) |
Source: KDP help, Create a Paperback Cover; KDP help, Set Trim Size, Bleed, and Margins. Read on 10 November 2026.
The limits in the table are the highest page counts any trim size allows for that paper. Large trim sizes stop sooner: see the page count limits.
Get the page count right first
The spine is only as right as the page count. KDP rounds an odd count up to an even number, and a change to margins or font size moves the count. The checker on this site works on the inside pages only: it reports the page count the printer will use and evens it. It does not check covers.
Check the page count of your interior PDF
Questions
What is the KDP spine width formula?
Page count times a thickness per page: 0.002252 in for white paper and standard colour, 0.0025 in for cream paper, 0.002347 in for premium colour. A 300-page book on white paper has a spine of 0.6756 in.
How many pages do I need for text on the spine?
At least 79. The KDP cover page says: "To include spine text, your book must have at least 79 pages."
Does the trim size change the spine width?
No. The spine depends on the page count and the paper. The trim size changes the width and height of the whole cover.
Why did my spine width change after I fixed the interior?
The spine follows the final page count. Adding a blank page to make the count even, or changing the font size, changes the count and so the spine. Finish the interior first, then size the cover.