It is important for us to know this parameter in advance when the publication has a spine that the cover wraps around – e.g. with books, ring binders and hidden-spiral products. The way the spine width is calculated differs from one product group to another, although there is a simple basic rule: the thickness of the front and back of the cover + the thickness of the leaves of the inside pages.
The number of leaves in the inside pages is usually half the number of pages, but publications where we print on only one side of the inside pages are not rare (Japanese fold book, thesis, notepad, etc.). It can also affect the result if the inside pages include a number of papers of different materials and thicknesses.
Let's go through it product by product:
Perfect-bound book
This is perhaps the easiest one to calculate: the number of inside pages (and this time including the ones left blank) has to be divided by two. With these products the most common choice is 80 g offset (uncoated) inside pages, of which 100 leaves, that is 200 pages, come to exactly 10 mm. The thickness of the cover is mostly negligible in this case (max. 0.5 mm).
Book with Japanese fold
This is where the exception comes in, because this structure is mostly chosen to make the inside pages look more substantial, so printing is done on only one side of the paper – so there are as many leaves as there are pages.
Thread-sewn book with hard cover
The inside pages are calculated the way we have already seen, but the cover is considerably thicker. The hard cover itself is made using 2 mm greyboard, and on top of that come the cover print and the endpapers. Together these usually add up to 5.5 mm.
With larger and more extensive publications it is not rare for us either to use 3 mm greyboard or to glue 2 pieces of 2 mm board together, so that an A3 book stays rigid even when it is lifted by its corner.
Saddle-stitched booklet
Although no print goes on the spine here, with inside pages that are more extensive and/or made up of thicker leaves, the thickness of the booklet can reach as much as 5-6 mm. This means that with a 20x20 cm size, for example, the 3 mm bleed is not enough for the cover, or the booklet has to be trimmed narrower.
You can find the thickness of the papers we offer for covers and inside pages in the online paper catalog.
