My print cover is the wrong size: fixing spine width errors on KDP, IngramSpark and Lulu

A print cover is one wide image: back cover, spine and front cover side by side, with bleed (a little extra picture that gets trimmed off) all the way round. The front and back are always the size of your book. The spine changes: it's as wide as the book is thick, and that depends on how many pages you have and which paper they're printed on. Change either one and the old cover no longer fits.

How the spine is worked out

KDP publishes a thickness per page (as at 4 October 2026):

A 300-page book on cream paper has a 0.75 in spine (300 × 0.0025). The same book on white paper is about 0.68 in. Switch paper, or add 20 pages, and the cover is wrong.

The full cover width is bleed + back + spine + front + bleed, and the height is bleed + trim height + bleed, with 0.125 in of bleed. A 6 x 9 in, 300-page cream paperback is 0.125 + 6 + 0.75 + 6 + 0.125 = 13 in wide and 9.25 in tall.

Lulu's paperback spine is the page count divided by 444, plus 0.06 in. IngramSpark doesn't publish a formula; its cover template generator gives you the exact spine and document size.

What the messages mean

KDP. The Print Previewer flags a cover that isn't the size it expects for your trim, paper and page count. KDP's help lists the usual causes: a cover built for the wrong paper, a white border left around the artwork, or a page count that changed after the cover was made. The cover must also be a single-page PDF with back, spine and front as one image.

IngramSpark publishes its wording:

• "Cover Layout Submitted is Not Built to the Correct Specifications": the cover was built for a different trim, paper or page count. IngramSpark says that if your page count goes up or down by more than four pages, you may need a new cover. Fix: make a fresh template with your current details and rebuild.
• "PDF Document Size is Incorrect": the PDF page as a whole doesn't match the document size on the template. Fix: make the PDF page exactly the template's size.

Lulu. Its cover upload message tells you the size of your file ("Your PDF dimensions are…") and the range it needs. Lulu allows a small tolerance, shown for your project. The cover must be one page. For retail distribution Lulu also needs a separate distribution cover with a slightly different spine, made from its own template.

How to fix it in Word

Finish the interior first. Every cover fix after that is quicker.

1. Get your final page count from the PDF, and check which paper you've chosen.
2. Get the correct full cover size from your platform's calculator or template (or Bervet's, below).
3. Go to Layout > Size > More Paper Sizes and enter the full cover width and height.
4. Move the artwork so the front cover sits on the right-hand side, the back on the left, and any spine text is centred in the new spine.
5. Delete any white border. The background should run to the page edge.
6. Save as PDF and check it has exactly one page.

Using a designer, InDesign, Affinity or Canva? Send your final page count, trim, paper and printer, and ask for the cover rebuilt on a fresh template. Ask again after any interior change.

Check before you upload

Bervet's free spine width calculator works out the spine and full cover size for each printer, gives you a template, and checks your finished cover PDF against it. The check runs in your browser and nothing is uploaded; checking a PDF needs a free Bervet account. Book trim sizes lists each printer's trims.