---
title: "Book spine width calculator — full wrap cover dimensions"
description: "Spine width and full wrap cover size for a paperback, from page count, trim and paper stock. Amazon KDP's own figures, in inches and metric."
source: https://usegalley.com/resources/book-spine-width-calculator
---
[Home](https://usegalley.com/) [Resources](https://usegalley.com/resources) Spine width calculator

# Book spine width calculator

Page count, trim size and paper stock in. Spine width out, in inches and metric, with the full wrap cover size for a paperback. The paper thicknesses are Amazon KDP's own published figures.

Binding

Page count Off the final interior PDF, not the manuscript.

Trim size Changes the wrap, not the spine.

Paper Most novels print black on cream.

Metric unit

Spine width

0.8 in 20.3 mm

Page count × paper thickness, and nothing else. Trim size is not in that
sum, so changing it moves the wrap and leaves the spine where it is. Trim
does change the spine, but only by changing your page count first:
[work that out here](https://usegalley.com/resources/word-count-to-page-count).

This runs entirely in your browser. Nothing you type is sent anywhere, and
there is no account to make.

## How to calculate spine width

**Spine width = page count × paper thickness.** The thickness of one printed sheet, which depends on the stock and not on the binding:

| Paper | Inches per page | Millimetres per page |
| --- | --- | --- |
| Black ink on cream | 0.0025 | 0.0635 |
| Black ink on white | 0.002252 | 0.0572 |
| Standard colour, paperback only | 0.002252 | 0.0572 |
| Premium colour | 0.002347 | 0.0596 |

### Spine width at common page counts

Black ink, the two paper stocks a novel is printed on.

| Page count | Cream paper | White paper |
| --- | --- | --- |
| 100 pages | 0.25 in / 6.3 mm | 0.225 in / 5.7 mm |
| 150 pages | 0.375 in / 9.5 mm | 0.338 in / 8.6 mm |
| 200 pages | 0.5 in / 12.7 mm | 0.45 in / 11.4 mm |
| 250 pages | 0.625 in / 15.9 mm | 0.563 in / 14.3 mm |
| 300 pages | 0.75 in / 19.0 mm | 0.676 in / 17.2 mm |
| 350 pages | 0.875 in / 22.2 mm | 0.788 in / 20.0 mm |
| 400 pages | 1 in / 25.4 mm | 0.901 in / 22.9 mm |
| 450 pages | 1.125 in / 28.6 mm | 1.013 in / 25.7 mm |
| 500 pages | 1.25 in / 31.8 mm | 1.126 in / 28.6 mm |
| 600 pages | 1.5 in / 38.1 mm | 1.351 in / 34.3 mm |

### Paperback

**Full wrap = bleed + back cover + spine + front cover + bleed.**
The bleed is 0.125 in on every outside edge, so the wrap is always 0.25 in
wider than the two covers plus the spine, and 0.25 in taller than the page.

Spine text has two rules on top. KDP refuses it under 79 pages, and above
that it wants 0.0625 in of clearance on each side of the text, because the
fold lands in a slightly different place on every copy.

### Hardcover

A case laminate cover is not a paperback with a thicker spine. KDP documents
three allowances and generates the finished canvas itself:

- **Wrap** of 0.51 in (15 mm) past every outside edge, which folds around the board and glues to the inside.
- **Spine hinge** of 0.4 in (10 mm) each side of the spine, where the case bends open. No text and no barcode goes in it.
- **Safe area** starting 0.635 in (16 mm) from the edge of the book.

What Amazon does not publish is how far the case board overhangs the book
block, and that number is inside the total cover size. So this gives you the
spine and the allowances, and their own cover template generator gives you
the canvas. Hardcover runs 75 to 550 pages, on white or cream, and standard
colour is not offered.

The page count is the input everything else hangs off, and it is the one most
people guess at. [Turn a word count into a page count](https://usegalley.com/resources/word-count-to-page-count) first if you do not have a laid-out interior yet.
Galley reads the real page count straight off the
[print PDF it builds](https://usegalley.com/docs/preview-and-export), so there is
nothing to guess.

Everything here is Amazon's, for Amazon. IngramSpark prints on different
stock and publishes its own template generator, and a spine width borrowed
from one printer and sent to another is how you get a cover with the title
creeping round onto the back.

**For working things out, not for signing anything.** Printers
and retailers set their own rates and specifications, change them without
notice, and none of them is affiliated with me or with Galley.
I checked these figures by hand in August 2026
against [KDP's paperback cover specification](https://kdp.amazon.com/en_US/help/topic/G201953020) and [its hardcover one](https://kdp.amazon.com/en_US/help/topic/GDTKFJPNQCBTMRV6).
Confirm on the official page before you commit money to a price, a
print run or a contract.

## Questions

How do I work out the spine width of a book? Multiply the page count by the thickness of one sheet of the paper you are printing on. On Amazon KDP that is 0.002252 inches a page for black ink on white paper and 0.0025 inches a page on cream. A 320 page novel on cream comes to a 0.8 inch spine, or 20.3 mm.

Is the page count the same as my Word document? No, and this is where most covers go wrong. The page count is the page count of the final laid-out interior PDF, at your real trim size and type size. It moves every time the text reflows. Set the interior first, then read the page count off it, then design the cover.

How wide does the spine need to be for text on it? On a paperback KDP will not print spine text below 79 pages. Above that, keep the text at least 0.0625 inches clear of each fold, because the trim shifts slightly on every copy. A hardcover has a 0.4 inch hinge on each side of the spine and nothing should sit in it.

Why does the hardcover not give me a full cover size? Because Amazon does not publish one. KDP documents the wrap, the hinge and the safe area, then generates the finished canvas with its own template tool, which also accounts for how far the case board overhangs the book block. So this gives you the spine width and the published allowances, and stops there.

Does this work for IngramSpark? No. Ingram prints on its own paper stocks with its own thicknesses, and it publishes a cover template generator that knows them. Use that one for Ingram rather than a number worked out from Amazon paper.

## Next

[Words to printed pagesThe page count this calculator needs.](https://usegalley.com/resources/word-count-to-page-count) [KDP royalty calculatorWhat those pages cost to print, and what you keep.](https://usegalley.com/resources/kdp-royalty-calculator) [Trim size comparisonSee what the trim does to the page count.](https://usegalley.com/resources/book-trim-size-comparison) [Cover template generatorThe same numbers, as a PDF you can draw on.](https://usegalley.com/resources/book-cover-template-generator)

More at [the resources index](https://usegalley.com/resources).

Put all this into practice when you write your novel in Galley.

[Launch Galley](https://app.usegalley.com)