Book Spine Width: Why It Matters and How to Calculate It
When you're preparing to print a perfect bound paperback book or a hardcover book, getting your spine width spot on is absolutely essential. The cover print file for PUR perfect bound books, hardcover books and dust jackets (as per our print specifications) need to be in a spread that includes the spine, between the back and front cover, so having that spine section of the print file in the right width is a non-negotiable.
The width of your spine will not only help you determine exactly how much text and imagery you can include in your book's exterior design, and make sure your book is printed and bound in the right size for the professional finish it deserves. If your spine width is off, even by a few millimetres, your cover artwork won't align properly when it's printed and bound.
For example, if the spine is too narrow, the book's front and back cover will start to show on the spine itself, and if the spine is too thick, the content you want only to be seen when it's sitting on a shelf will creep into the front and back cover design. Sending your book to print with the wrong spine width will often push back your printing timeline while you or your designer have to correct the print file and resupply it, which makes hitting deadlines difficult and delays getting your books into readers’ hands.
Calculate a Book’s Spine Width Instantly
For years, we’ve been calculating the book spine’s width for clients and after a while, it just made sense to make an easy tool that can be used by everyone, internally and externally to figure it out quickly and easily.
All you’ve got to do is input your total page count, select your preferred internal and cover paper stock and weight from our paper range, and voila! The calculator will provide a precise spine width in millimetres that you or your book cover designer can use to finalise print files.
How to Calculate a Book’s Spine Width Manually
If you’ve got a different paper stock in mind or you’d simply like to try calculating it for yourself, you can figure out the spine width of a book with the following three things:
- Your internal page count (that's every page inside your book, excluding the front and back cover; usually 4 pages)
- The thickness of your internal paper stock (in millimetres)
- The thickness of your cover stock (in millimetres)
The formula to calculating a book spine width manually is:
Spine width (mm) = ((number of internal pages/2) * paper stock weight (mm)+ (2 x cover stock weight (mm))
This means that you're dividing your internal page count by two (because each sheet has two pages), multiplying that by how thick each sheet of paper is, then adding the thickness of both your front and back covers. The spine width calculator above uses this same formula, except that you can input the total page count of your book as it’ll manually deduct the cover pages for you. Many printers will also flatly add 0.7mm instead of the specific book cover page thickness, but this formula is a bit more specific and hopefully will be more accurate for your project’s spine width.
Paper Weight vs Paper Thickness
While gathering information to calculate spine width manually, it’s worth noting that although paper is generally measured in gsm (grams per square meter), this is not the thickness of the paper but the weight. While it’s true that heavier paper stocks will usually correlates with being on the thicker side, the thickness and weight is not universal and is very dependent on the paper type, brand and finish used.
Paper stock thickness (not weight) is measured in microns (μm), which is why we’ve included the thickness next to the corresponding weight (gsm) for stocks in our paper range. If you're wondering what a micron is and how you can convert it to a millimetre, simply divide it by 1000, or move a decimal point 2 spots to the left.
If you’re not sure about which paper to use (and this will obviously affect your spine width), feel free to get in touch to request a paper sample book.
Spine Width Advantages & Guidelines
The spine of any book is often the only part visible to readers when it's sitting on a shelf, so you want to take advantage of that real estate to make your book stand out by showcasing the title, author, year, brand and/or publisher. Having the correct spine width for your print file is therefore not only crucial for your books’ structural integrity, but it's prime marketing real estate for when your book is spine-out on a bookshelf.
It’s good to keep in mind that both the formula for manual calculation and the calculator above are meant as guidelines, rather than a guarantee, because other factors such as the binding method and other special finishes (die cuts, flaps, etc), can nudge the final measurement slightly. However, a close estimate is much better than a wild guess that could delay printing and delivery. PUR perfect binding machines also have certain width requirements and when printing with us, your book's spine width needs to be at least 3mm wide.
If you’re not sure about your book’s spine width or have any questions, we’re also only a quick form submission away! Simply request a quote online or fill in our contact form to get a callback from one of our print experts.