What is paper basis weight? It can be a complex topic. We are working on some guides to place on in the reference section of our site. Until then, here is an excerpt from the International Paper "Pocket Pal -19th Edition" that may help you:
Basis weight identifies printing papers, with few exceptions. In the United States, it is the weight in pounds of a ream (500 sheets) in the basic size for that grade. In the metric system, it is the weight of one square meter of paper and is expressed in grams per square meter or g/m2. Basis 70 means that 500 sheets 25 x 38 inches of book paper weigh 70 pounds. This is equivalent to 104 g/m2 in the metric system.
In the U.S. system, the basic size is not the same for all grades: It is 25 x 38 for book papers (coated, text, offset, opaque, etc.); 17 x 22 for writing papers (bond, ledger); 20 x 26 for cover papers (coated and uncoated); 25.5 x 30.5 for index bristol, 22.5 x 28.5 or 22.5 x 35 for mill bristol and postcard; 24 x 36 for tag and newsprint.
Paper is commonly identified by ream weight: 20-pound bond, 70-pound coated, etc. However, paper is usually listed in size-and-weight tables and price lists on a thousand sheet basis: 25 x 38 -- 140M for a 70-pound book paper, the "M" meaning 1,000 sheets 25 x 38 weighs 140 pounds. Each grade is made in many standard sizes other than the basic size, and in many weights. Ffor example, book papers are made in weights from 50-pound to 100-pound in 10-pound increments.
From our site. We some tools that can help you measure basis paper weight.
Check out our Pocket Paper Scale
and our Premium Basis Weight Paper Scale.