Believe it or not, at the beginning of the 90s, in the distant twentieth century, there was no computer with programs to help the designer in the production of some graphic material. In fact, there was no computer. At least not within reach of a mere mortal like me.
The work was done by hand, almost artisanal. That is, the monitor at that time was the paper itself.
When we created a book cover, for example, one of the most annoying things was calculating the width of the spine. Something that was often done on the eye.
For that, you had to know the number of pages, whether the cover would be hard or flexible, take into account the weight of the paper, delve into mathematical formulas, and finally pray that the title and author of the book, which is almost always placed vertically, they were right there, right in the middle of the spine.
If, on the one hand, this could represent an uncreative task, on the other hand, life without a computer forged a more refined look in design professionals.
Today things are much easier. We can leave the math aside. And to make it even easier, there are some graphic sites and print shops that help solve this problem.
Several of them have an online calculator that determines the dimensions of the spine. Just enter the total number of pages, choose the paper type, select the cover dimensions and you’re done. Immediately it indicates the width.
On American sites, measurements are in inches (sometimes Americans like to complicate people’s lives, and that’s why they don’t work with millimeters or centimeters).
Of course, depending on the complexity of your project, the ideal is to check these values directly with the printing company where your book will be printed. Because they all have their production methods and procedures.
But always consider that a book with less than 70 pages is too thin to have a spine.
This reminds me of an amusing chronicle by the late Brazilian writer João Ubaldo Ribeiro, where he writes that his grandfather did not take seriously a book that did not stand up on its own: “This is shit.”, said the old man. “These booklets that don’t stand up aren’t books, they’re leaflets”.