Front cover, back cover and spine. Those are the elements of a perfect bound print book jacket. The front and back cover dimensions, called the trim, will be the same as your final print size (plus any bleed determined by your printer), but how do you calculate spine width?
To calculate spine width, you need to know the final page count when printed. It’s as simple as that. Well, sort of. The paper weight of the interior pages and cover will also be a factor. For this reason, it’s important to always ask your printer to give you a formula to calculate spine width.
How do page count and paper weight determine the spine width? It’s easy to understand if you visualize your book in it’s final printed form. The more pages in your book, the thicker the spine. If those pages are on a heavier paper, the spine width increases. Conversely, if the paper is lighter weight, the spine width decreases.
Calculating page count
If this is your first publishing project, you may be tempted to based your page count on your manuscript. If you’ve written your manuscript in Word or some other word-processing program, you’ll have a page count. But for printing and to calculate spine width, you need to know the page count of your book in its final printed form. And this will depend on the dimensions you choose for your printed book.
Again, visualize how page counts work. If your manuscript is formatted on a standard word processing document with standard margins, it’s likely going to print nicely on standard A4 or A5 paper from your home printer. But it’s unlikely that you are going to choose this size for your printed book, and you need to take binding into account. You, or a professional designer you’ve hired to lay out your book’s interior pages, will select a trim size. This final dimension will change the number of pages in your book. It may be more or less, depending on the trim size.
Then, you must take into account margins, which will change as you decide how to design the interior pages. You may want a larger margin at the top with a running header of the book’s title, author name, or both. If you decide to place the page numbers at the top as well, you may have a narrower margin at the bottom of the page. You’ll need a wider margin near the spine to account for your desired margin plus the fold of the book as the page count increases.
All of these margin changes are going to affect the final page count of your book.
Finally, your book will likely include a title page, perhaps a table of contents, acknowledgements, and/or dedication page. You may have an About the Author page at the end of the book, or a glossary or index. All of these pages, including any blank pages, must be included in the final page count.
A few other considerations will be whether your book is hard or soft cover and what type of materials are used for the cover.
Calculate Spine Width
Once you’ve taken all of the above into consideration, it’s time to calculate spine width for your book cover. You may note that you need to have a final layout of your book’s interior before you can calculate spine width.
You’ll also need printer specifications, including paper weight and cover paper weight. The best solution is to simply ask the printer for a formula to calculate spine width based on your book’s page count.
If you are self-publishing, you are likely using a print on demand solution such as Createspace or Lightening Source (Ingram). Createspace uses 50-pound white or cream paper for black and white interior books. Ingram’s standard is 60-pound white or cream paper. Let’s take a look at the differences in spine width for each:
- Createspace: 190 pages, black and white interior, on 60-pound white paper = spine width 0.42788 inches
- Ingram: 190 pages, black and white interior, on 50-pound white paper = spine width 0.404 inches
Download my free PDF “Calculate Spine Widths” for a chart with standard spine widths already calculated for you based on rounded page counts. You can print this PDF or save it to your computer for quick reference.