The printer charges for every page printed, including the blank ones, and those with roman numerals. In addition, the page count is taken into consideration when shipping is calculated because that affects the weight of the book. So, we must always list the actual total number of pages in the book.
If your book has 10 pages of roman numerals at the beginning, yet the page number on the very last page of your book is 250, your book actually has 260 pages. In order to view the actual page count of your book, look at the total number of pages listed in the final pdf version of your interior file. The book below has 422 physical pages.
