Paper
Calculating
Calculating Spine Width for book design
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There are 500 standard sheets in a ream. Standard book sheets are 25” x 38”. The paper weight is the weight of a ream. Referring to 50 lb. paper means that the ream it came from weighed 50 lb. Common weights for paper used in novels and non-fiction books are 45 lb., 50 lb., 55 lb., and 60 lb.
The thickness of paper is known as caliber. PPI is the abbreviation for Pages Per Inch. The thicker the paper the lower the PPI. Pages per inch is important when calculating the spine width. If you are having a graphic designer create your print files, he or she will calculate this for you.
Papers are either coated or uncoated. Uncoated papers are typically used in novels and non-fiction books. Books that have images like children’s picture books and photo books will have coated paper. This smooth-to-the-touch paper is used for its opacity as it is better for presenting images. The materials used in coated paper make it heavier. Commonly used coated paper weights are 80 lb. and 100 lb. Coated paper can come in different sheens such as matte
finish or gloss finish. Matte paper is recommended for children’s picture books due to its lower reflectivity. Photo books typically have gloss paper to give the images deeper, more vibrant color.
Non-fiction books will normally have a stark white paper. Novels, which are read for longer blocks of time, will usually have off-white (cream) paper which is easier on the eyes.
Page Per Inch (PPI) Formula
Thickness is measured in Pages Per Inch (PPI).
PPI is calculated by this formula:
How to calculate spine width for a 50lb white opaque stock, ppi is 513
If your book is 256 pages
256 ÷ 513 = 0.5048 (spine width is .50)
How to calculate spine width for a 60lb white opaque stock, ppi is 426
If your book is 256 pages
256 ÷ 426 = 0.6009 (spine width is .60)
How to calculate spine width for a 55lb Cream stock, ppi is 360
If your book is 256 pages
256 ÷ 360 = 0.7111 (spine width is .71)
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How to calculate spine width for a 60lb Cream stock, ppi is 450
If your book is 256 pages
256 ÷ 450 = 0.5688 (spine width is .56)
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This is for a paperback cover only.