Letter (paper size) "official" "Government Letter" size, , was used in government, while paper was standard in most other offices. In the U.S., paper density is usually measured in "pounds per ream" (of 500 sheets). Typical Letter paper has a basis weight of paper of – the weight of 500 sheets (a ream) of paper at and at 50% humidity. One ream of 20-pound Letter-sized paper weighs , and a single Letter-sized sheet of 20-pound paper weighs , which is equivalent to 75.19 g/m. Some metric information is typically included on American ream packaging. For example, 20-pound paper is also labeled as 75
Inkjet paper include coatings engineered to receive and hold ink. Fine art papers are usually made of rag pulp (100% cotton being the most common) but may also be have an alpha-cellulose base. Some descriptions and comparisons of fine art inkjet papers are here, here, here, and here. Some fine art papers are mold made, while others are machine made, and may vary considerably in surface texture. Many fine art papers are available in pre-cut sheets or in rolls. Standard office paper has traditionally been designed for use with typewriters and copy machines, where the paper usually does not get wet. With