Book Cover Size Calculator
The book cover size calculator helps bookbinders, journal makers, and craft binders determine the exact dimensions for a book cover including spine width, board size, and the total cover material dimensions. Getting these dimensions right is critical in bookbinding: a cover that is too small will not protect the text block, and a spine that is miscalculated will not close properly. This tool calculates the spine width from page count and paper thickness, adds the standard board overhang (square), and includes the turnover allowance to give you the total cover sheet dimensions to cut.
Book cover formula
Spine width (mm) = (Pages / 2) x Paper thickness per sheet
Board width = Page width + Board square
Board height = Page height + (2 x Board square)
Total cover width = (2 x Board width) + Spine + (2 x Turnover)
Total cover height = Board height + (2 x Turnover)
Frequently asked questions
How do I calculate the spine width of a book?
Spine width = Number of pages x Paper thickness (per sheet) / 2. Because a single sheet has two sides (pages), divide by 2 to get sheet count, then multiply by paper thickness per sheet. Add the thickness of both endpapers. For a 200-page book using 0.1 mm paper: 200/2 x 0.1 = 10 mm spine. Adding a cover board thickness (2-3 mm) on each side is optional for case binding.
What is the turnover allowance in bookbinding?
The turnover allowance is the extra material on the cover that wraps around and adheres to the inside of the cover boards (the 'turn-in'). A typical turnover is 15 to 20 mm on each edge. For a standard hardcover, 18 mm (about 3/4 inch) per side is common.
What are the standard book cover boards dimensions?
Cover boards typically extend 3 mm (about 1/8 inch) beyond the text block on the top, bottom, and fore-edge. This overhang is called the 'square' or 'square-off'. So the board height = page height + 6 mm, and board width = page width + 3 mm (front or back, not spine).
What thickness of paper should I assume?
Standard copy paper (80 gsm) is approximately 0.1 mm thick. Text-weight printing paper (60-70 gsm) is 0.08 to 0.09 mm. Heavier paper (90-100 gsm) is 0.11 to 0.12 mm. If you know the caliper of your paper, use that value for the most accurate spine width calculation.
How do I calculate the total cover sheet size?
Total cover width = Front board width + Spine width + Back board width + 2x turnover. Total cover height = Page height + 2x board square + 2x turnover. This is the total material size you need to cut from your cover material (paper, bookcloth, leather, etc.).
Sources
- Library of Congress: LC - Care, Handling, and Storage of Books.
- Guild of Book Workers: Guild of Book Workers - Standards and Education.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.