Calculation of paper and cover paper

The text is calculated on paper:
The number of reams needed to print a book can be calculated from the number of pages (1 page = 2 faces), number of impressions, and number of open pages.

Text paper number = number of pages × number of prints / (number of opening × 500)

Text paper number = print number × print sheet / 1000

Print sheet=face number/opening number

Cover paper calculation:

Calculate cover paper and text paper differently. The paperback cover must be attached to the back cover and spine. The width of the spine is narrow and narrow, and some paperbacks still have a mouthful, which inevitably affects the amount of paper used in the cover.

Cover paper number = print number / (cover sheet opening number × 500)