Internet, Networking, & Security Web Development The Definition and Purpose of Basis Weight Eliminate the Paper Weight Confusion By Jacci Howard Bear Writer A graphic designer, writer, and artist who writes about and teaches print and web design. our editorial process Jacci Howard Bear Updated July 09, 2018 Getty Images Web Development Web Design CSS & HTML SQL Tweet Share Email The weight, measured in pounds, of 500 sheets of paper in that paper's basic sheet size is its basis weight. Even after the paper is trimmed to a smaller size, it is still categorized by the weight of its basic size sheet. However, the basic sheet size is not the same for all paper grades, which causes confusion when comparing different types of paper and their weights. Examples When 500 sheets of bond paper at its basic sheet size of 17 x 22 inches weighs 20 pounds, that paper is still identified as 20 lb. paper even after it is trimmed to the familiar 8.5 x 11-inch size.When 500 sheets of cover stock at its basic sheet size of 20 by 26 inches weighs 65 pounds, the cover stock is still referred to as 65 lb. cover even when trimmed to a smaller size. Basic Sheet Sizes for Different Types of Paper Bond, copy paper, ledger paper and rag paper all have a basic sheet size of 17 x 22 inches.Offset, book, text and coated papers have a basic sheet size of 25 x 38 inches.Cover stock has a basic sheet size of 20 x 26 inches.Tag stock has a basic sheet size of 24 x 36 inches.Index stock has a basic sheet size of 25.5 x 30.5 inches.Bristol stock has a basic sheet size of 22.5 x 28.5 inches. Because the basis weight is based on sheet sizes that differ among types of paper, basis weight alone isn't sufficient for choosing a paper. An 80 lb. text paper is not the same as 80 lb. cover, for instance—it is much lighter weight. You need to know if you're talking about bond paper or cover paper or one of the other types of paper to compare them by weight. Only with papers that share the same basic sheet size, can weights be compared directly. If you are in the office supply store and see reams of bond paper identified as 17 lb., 20 lb. and 26 lb. paper, you can be confident that the 26 lb. paper is thicker—and probably most costly—than the other choices.