When we measure a book, it’s the inside page dimensions we are referring to (NOT the outer hardcover dimensions). So if we are discussing an 8.5 x 11″ hardcover, the actual outer dimensions of the book are 8.75″ x 11.25″ . See the digaram below for further explanation.
Here is an example of a hardcover template diagram for an 8.5″ w x 11″h page size book with the minimum spine thickness (0.375″). This spine size covers most children’s books and yearbooks of smaller page counts. As a book gets thicker in page count ( beyond the 0.375″ thickness, we can advise an exact spine size based on which type of paper is selected and the final page count. We have a “caliper sheet” below with a formula on spine width calculations. If ever any question, please contact firstname.lastname@example.org
Formula for Calculating Spine Width
This is for books that exceed 0.375″ thickness in text bulk. Take the number of pages divided by 2. Then multiply by the paper thickness and add .125″
Example: 200 pages text on 100 lb Silk text
Take the number of pages divided by 2: 100/2 = 100
Then multiply by the paper thickness: 100 x 0.0058 = 0.58″
and add .125” : 0.58 + 0.125