The spine is the visible edge of your book when it sits on a shelf. KDP calculates spine width based on how many pages your book has and the type of paper used. If the spine is too narrow, Amazon will not print text on it. A wider spine (usually 100+ pages on white paper) allows your title and author name to appear on the spine.

Amazon KDP multiplies your total page count by the paper thickness constant for your chosen paper type:

• White Paper: 0.002252″ per page
• Cream Paper: 0.0025″ per page
• Color Paper: 0.002347″ per page

For example, a 300-page book on white paper has a spine of 300 × 0.002252 = 0.6756″.

KDP requires a minimum spine width of 0.0625 inches (1.59 mm) before spine text is allowed. This typically means your book should have at least 100 pages for white paper. If your spine is thinner, leave it blank in your cover design.

Your full cover file must include the back cover, spine, and front cover as one flat image. The total width is calculated as:

Full Cover Width = (2 × Trim Width) + Spine Width + Bleed

KDP adds 0.125″ of bleed on the left and right edges if you choose “With Bleed”, which is recommended for professional print quality.

White paper is standard for most books and is the default. It’s bright white, which makes text and images pop. Cream paper is preferred for novels and fiction — it’s easier on the eyes for long reading sessions. Color paper is for full-color interior books like children’s books or photo books.

No. This is an independent, free tool built to help authors and publishers calculate KDP specifications. Always verify the final numbers on your official KDP dashboard before submitting your cover file.