Free tool
Book spine width calculator
Type the page count, pick the house and the paper, and get the spine width, whether the spine can carry text, and the full size of the cover wrap with bleed.
Runs in your browser. No sign-in, and nothing you type leaves this page.
- Spine width
- 0.54 in · 13.7 mm
- Amazon KDP’s published formula.
- Spine text
- Allowed
- Amazon KDP: text from 79 pages.
- Full cover wrap, with bleed
- 12.79 in × 9.25 in
- 324.9 mm × 234.9 mm. 0.125 in bleed on each outside edge, 6 × 9 in trim.
How it works
A paperback spine is the thickness of the paper block, so every house works it out the same way: the number of interior pages times the thickness of one page. Amazon KDP publishes its figures on its cover help page: 0.002252 in a page for black ink on white paper, 0.0025 in on cream, 0.002252 in for standard colour and 0.002347 in for premium colour. A 300-page novel on cream paper is therefore 300 × 0.0025 = 0.75 in.
Lulu uses a different formula for a perfect-bound paperback: the page count divided by 444, plus 0.06 in. The fixed 0.06 in is why a Lulu spine is always a little wider than a KDP spine for the same pages. IngramSpark and Barnes & Noble Press do not publish a per-page figure; each one gives the spine through its own cover template generator. For those two houses this page uses the standard 50 lb white and crème thickness, which is the same as KDP’s, and labels the result as an estimate. Before you send a cover to either house, download its template for your exact page count.
Spine text has its own floor. KDP allows it from 79 pages and asks for at least 0.0625 in of space between the text and each edge of the spine. Lulu’s guide says to leave the spine blank at 80 pages or fewer. IngramSpark does not print spine text under 48 pages. Below those counts the spine is too narrow for type to land reliably, because the fold can drift by a sixteenth of an inch either way.
The cover wrap is one flat image: bleed, the back cover, the spine, the front cover, and bleed again. KDP writes it as bleed + back + spine + front + bleed for the width and bleed + trim height + bleed for the height, with 0.125 in of bleed on every outside edge. A 6 × 9 in book with a 0.5 in spine is 0.125 + 6 + 0.5 + 6 + 0.125 = 12.75 in wide and 9.25 in tall. Keep text at least 0.125 in inside the trim on KDP, and 0.25 in on IngramSpark.
Count every page in the interior PDF, including the title page, the copyright page and any blank pages. If the count changes after the cover is made, the spine changes with it, so finish the interior first and make the cover last. The KDP trim and margin checker gives the inside margin for the same page count.
Read the guide
Questions
How wide is the spine of a 200-page book?
On KDP, 200 pages of black ink on white paper make a 0.450 in (11.4 mm) spine; on cream paper it is 0.500 in (12.7 mm). Lulu adds a fixed 0.06 in, so the same 200 pages are 0.510 in there.
How many pages does a book need for text on the spine?
KDP allows spine text from 79 pages (Cover Creator asks for 80). Lulu says to leave the spine blank at 80 pages or fewer. IngramSpark does not print spine text under 48 pages.
Why is my cream-paper spine wider than white?
Cream paper is thicker. KDP measures it at 0.0025 in a page against 0.002252 in for white, so a 300-page book is about 0.07 in wider on cream.
Is this the exact number to build my cover with?
For KDP and Lulu it uses the house’s published formula. For IngramSpark and Barnes & Noble Press, which publish no per-page figure, it is an estimate: download the house’s cover template for the final file.
Does the page count include blank pages?
Yes. Count every interior page in the PDF, front matter and blank pages included. The houses print an even number of pages.
Format the whole book on the WriterDesk
The desk draws the front, spine and back while you write, with the spine estimate following the chapters and the barcode in place.
Open the WriterDesk