# How big should my book cover be?

Works out the full wraparound cover size and spine width of a print-on-demand paperback from its trim size, page count and paper, by the Amazon KDP formulas with a 0.125 in bleed.

- Page: https://www.acalculator.org/everyday-life/kdp-cover-calculator
- JSON spec: https://www.acalculator.org/everyday-life/kdp-cover-calculator.json
- Version: 9cb71f7f0934

## Default answer

Example with the default inputs (Trim width 6 in, Trim height 9 in, Page count 300, Ink and paper Black ink, white paper): The full cover is 12.926 in wide and 9.25 in high, with a 0.676 in spine.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| w | Trim width | The width of one page of the finished book, such as 6 in. |
| h | Trim height | The height of one page of the finished book, such as 9 in. |
| pages | Page count | The number of pages in the interior file (each side of a sheet is a page). |
| paper | Ink and paper | The interior ink and paper type, which sets how thick each page is. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| coverWidth | Full cover width (in) | Bleed + back cover + spine + front cover + bleed, in inches. |
| coverHeight | Full cover height (in) | Bleed + trim height + bleed, in inches. |
| spine | Spine width (in) | Page count × the paper thickness per page, in inches. |
| coverWidthMm | Full cover width (mm) | The full cover width in millimeters (inches × 25.4). |
| coverHeightMm | Full cover height (mm) | The full cover height in millimeters. |
| spineMm | Spine width (mm) | The spine width in millimeters. |
| spineText | Spine text | Whether text is allowed on the spine: only with at least 79 pages. |
| textArea | Spine text area width (in) | The spine width minus 0.0625 in on each side, the room left for spine text. |

## Method

spine = pages × thickness (0.002252 in white or standard color, 0.0025 in cream, 0.00235 in groundwood, 0.002347 in premium color); width = 0.125 + trim width + spine + trim width + 0.125; height = 0.125 + trim height + 0.125.

## Assumptions

- A paperback with a 0.125 in (3.175 mm) bleed on every outside edge, as KDP asks for.
- Page count ranges are KDP’s for most trim sizes; large trims such as 8.5 × 11 in allow fewer pages.
- Typed sizes are read exactly, so sizes typed in millimeters convert exactly (1 in = 25.4 mm).
- Check KDP’s own cover template before you upload; KDP may change its paper thicknesses.

## Worked examples

1. w = 0.1524, h = 0.2286, pages = 300, paper = white gives spine = 0.6756, coverWidth = 12.9256, coverHeight = 9.25, spineText = Allowed (79 pages or more), textArea = 0.5506. Source: Amazon KDP Help, Create a Paperback Cover (spine width = page count × 0.002252 in for white paper, 0.0025 in for cream, 0.002347 in for premium color, 0.002252 in for standard color; cover width = bleed + back + spine + front + bleed; bleed 0.125 in; spine text needs at least 79 pages and 0.0625 in from each spine edge), https://kdp.amazon.com/en_US/help/topic/G201953020 (retrieved 2026-10-02).
2. w = 0.1397, h = 0.2159, pages = 200, paper = cream gives spine = 0.5, coverWidth = 11.75, coverHeight = 8.75, coverWidthMm = 298.45. Source: Amazon KDP Help, Create a Paperback Cover (spine width = page count × 0.002252 in for white paper, 0.0025 in for cream, 0.002347 in for premium color, 0.002252 in for standard color; cover width = bleed + back + spine + front + bleed; bleed 0.125 in; spine text needs at least 79 pages and 0.0625 in from each spine edge), https://kdp.amazon.com/en_US/help/topic/G201953020 (retrieved 2026-10-02).
3. w = 0.2159, h = 0.2794, pages = 60, paper = premium gives spine = 0.14082, coverWidth = 17.39082, spineText = Not allowed (under 79 pages). Source: Amazon KDP Help, Create a Paperback Cover (spine width = page count × 0.002252 in for white paper, 0.0025 in for cream, 0.002347 in for premium color, 0.002252 in for standard color; cover width = bleed + back + spine + front + bleed; bleed 0.125 in; spine text needs at least 79 pages and 0.0625 in from each spine edge), https://kdp.amazon.com/en_US/help/topic/G201953020 (retrieved 2026-10-02).
4. w = 0.1524, h = 0.2286, pages = 400, paper = groundwood gives spine = 0.94, coverWidth = 13.19. Source: Amazon KDP Help, Paperback Submission Guidelines (groundwood paper: page count × 0.00235 in), https://kdp.amazon.com/help?topicId=G201857950 (retrieved 2026-10-02); Amazon KDP Help, Set Trim Size, Bleed, and Margins (page counts 24 to 828 white, 24 to 776 cream, 24 to 812 groundwood, 72 to 600 standard color, 24 to 828 premium color for most trim sizes; bleed 0.125 in), https://kdp.amazon.com/en_US/help/topic/GVBQ3CMEQW3W2VL6 (retrieved 2026-10-02).

## FAQ

### How do I calculate the spine width of a paperback?

Multiply the page count by the thickness of one page. KDP gives 0.002252 in per page for white paper, 0.0025 in for cream, 0.00235 in for groundwood, 0.002347 in for premium color and 0.002252 in for standard color. A 300 page book on white paper has a 300 × 0.002252 = 0.6756 in spine.

### How wide is the full cover?

The cover is one image of the back, the spine and the front, plus a 0.125 in bleed on the outside edges: width = 0.125 + trim width + spine + trim width + 0.125. For a 6 × 9 in book with a 0.6756 in spine that is 12.9256 in, and the height is 9 + 0.25 = 9.25 in.

### Can I put text on the spine?

Only if the book has at least 79 pages. Below that the spine is too thin and KDP rejects spine text. Keep the text at least 0.0625 in (1.6 mm) from each spine edge, so the calculator also shows the spine width minus 0.125 in.

### Why does the paper type change the cover size?

Each paper has a different thickness, so the same page count makes a different spine. 200 pages is a 0.4504 in spine on white paper but 0.5 in on cream, and the full cover grows by the same amount.

### What is bleed?

Bleed is extra artwork past the trim line, so the printed color reaches the edge after the book is cut. KDP asks for 0.125 in (3.2 mm) on the top, bottom and outside edges of the cover. Keep text and important art away from the trim line.

### Does this work for hardcovers?

No. Hardcover cases wrap around boards and use other sizes. This calculator follows the paperback cover rules only.

## Sources

- Amazon KDP Help, Create a Paperback Cover (spine width per page for each paper; cover width and height formulas; 0.125 in bleed; spine text from 79 pages and 0.0625 in from the spine edges). https://kdp.amazon.com/en_US/help/topic/G201953020 (retrieved 2026-10-02)
- Amazon KDP Help, Paperback Submission Guidelines (groundwood paper: page count × 0.00235 in). https://kdp.amazon.com/help?topicId=G201857950 (retrieved 2026-10-02)
- Amazon KDP Help, Set Trim Size, Bleed, and Margins (page count ranges per paper type). https://kdp.amazon.com/en_US/help/topic/GVBQ3CMEQW3W2VL6 (retrieved 2026-10-02)